How I Vibe Coded a $900K App in 13 Minutes (Claude Design + Codex)

I just cloned an app that makes $340 million a year, and I did this in just about 15 minutes. This is Calendly, a booking app that is worth about $3 billion now, and most of you watching have probably used it or at least heard of it. And today I want to show you how I built it using AI in just plain English. Not just a prototype, but a completely working app. You're able to make bookings, connect to a calendar, you can allow people to log in. Basically, any feature that Calendly has, I got it. So, if you've been thinking about building an app, this video's for you. And no, you don't need to be technical cuz I never touched a single line of code when building this app. If you use Claude or ChatGPT before, you can absolutely do this. I'm going to walk you through every single step. So, by the end of this video, you'll be able to vibe code your own calendar booking app, or any app for that matter. And if you have a Calendly subscription, I might just save you 30 bucks a month after you watch this video. Now, before we build this, I want to tell you why apps is such a great business model to be in. Number one, recurring revenue. People pay you every month to just keep using the app. So, think about your Amazon Prime subscription, for example. Amazon does not have to convince you to pay again and again every month. You just keep paying. And the second benefit is that you can sell it one day. You know, once your app starts making money every single month, you can sell it for a nice chunk of cash. And if you're curious on what apps are being sold, you can go to marketplaces like Flippa or Acquire.com, or even TrustRadius.com here, where you can see how much apps are being sold for and how many offers they get, etc. Now, you're probably thinking Calendly is worth $3 billion, and they probably got a huge team, they're well-funded. How can anybody compete with that? Well, what if I told you that there are tons of other players, and they're making good money as well. So, we've got Cal.com here, another big player. They just got $32 million in funding. So, it shows that there's a huge growing market for an app like this. But we've also got smaller players like TidyCal here, who hit a million dollars in revenue. Now, this data is or this article is couple of years old, and they probably make more now. And if I see something like this and I want to do something similar, here's the the that I would ask, you know, what is my unique angle? Where is my entry point? Or what if you can take this same idea, but maybe target a specific demographic? Cuz that's exactly what this app did, Book Like a Boss. They went after a more targeted demographic. Same idea, but they made themselves unique, and they actually made $1.4 million in revenue in 2024. So, if you're a solo founder, I think $1.4 million is really not a small number. So, I think this is the opportunity today in 2026, and let's not waste any time, and I'm going to show you how to build something like this. All right, so today we're going to be using two tools to build this app. We're going to use Claude design to build the front end of the app. This is currently the best tool for any type of design, cuz you can just use one prompt, and it will just give you amazing results. And then we're going to use ChatGPT Codex to build the back end functionality of the app. Now, the reason why I'm using Codex for this is that I've been playing around with this tool since the brand new in ChatGPT 5.5 model came out last week, and honestly, I've been quite impressed with the performance. And one major advantage is the fact that ChatGPT has the image tool built in, and I think that's where Claude is lacking. It doesn't have its own image generation model, so when you need to generate images, you got to pay for a separate subscription to Nerf Banana. So, everything's not in one place. Secondly, Codex combined with GPT 5.5 is currently the smartest model as of the recording of this video, and this is super important, especially when you're building an app like this. Now, of course, you can absolutely use Claude code to build an app, cuz everything that I'm going to be showing you today will be the same on whatever tool you use, but it's just that the interface will be slightly different. And if all of this doesn't make sense now, I promise you I'm going to walk you through every step of the way, and that's actually pretty easy. So, if you don't have the Codex app already, go ahead and download for the desktop app. I already have Codex installed here, so there's a couple of things that you want to set up. The first thing is that you want to go to settings, and you want to enable browser use and computer use, right? And this will allow Codex to actually go into your computer or open a Chrome browser and it's just going to give you a more seamless experience when you're building apps like this. Now, the second thing you want to do is you want to connect to a folder. Now, since we're building a web application, it's going to create HTML files, it's going to create assets, everything that's related to this project. So, you want to have a dedicated folder, just an empty folder that you don't mix with your other files. So, we keep everything separate so when we try to publish this on the internet, it's going to be a lot simpler cuz everything is just in one folder. So, if you look here, I have already connected it to a folder. So, obviously if you're doing this for the first time, you want to click here and you add new project and just select the empty folder that you create for this project. So, I'm going to connect it to this folder that I created called the Meetly app. And by the way, we'll just call the app that we're building Meetly. Now, for the model, I like to use the latest one here, GPT 5.5. That is the latest model that was just released and it's actually smarter than Opus 4.7. So, that is the model we're going to use today to build the app. Now, if you look to the left here, since I've already connected a folder to the Meetly app folder here, it's going to show up under projects. So, everything that we're doing related to this app will actually show up under this folder here. So, it just keeps everything organized and I think that's a better way of working. All right, so let's start prompting. Now, the first step that I take whenever I want to create an application is obviously think about the features that you want to have. Now, obviously you can do your own research, but you can ask Codex as well to give you suggestions, right? So, you can prompt it like this. I want to create a web application similar to Calendly or Cal.com and I want you to suggest a list of features that should be available in an app like this. So, just give me some ideas first and then I also want it to give me the data or the result in a numbered format so I can just pick and choose the features that I want. And now it's going to run and just give me all the features that it thinks I should have. All right, so it gave me like 30 different features here, which I think it's a quite a lot. So, I did ask it to narrow it down to just give me 10 features. So, let's run through this real quick. So, user accounts with profile management, yes, I want that. Public booking pages with custom links, calendar integrations, I want that. Event types, yes. Time zone aware scheduling, yes. So, all of these look like what I would see on Calendly. So, I'll just prompt it again. I want all these features, and I also want the ability to have a Google login, so users can log in and also connect to a Google calendar, right? Now, the next thing that I want it to do is actually to give me some samples of what the design will look like, right? So, we before we connect everything and make the back end works with the functions, I want to see some samples of the UI, and I want it to use the latest GPT-2 to design the UI. Use your image gen model, GPT image 2, to design the UI interface first. Give me five different UI options. Each option should include the host dashboard and the booking page for the guest, right? So, I want two different things here, and I do want five different image files, so I can just choose the one that I want. And then I'm going to hit go. So, this is what I mentioned earlier. That's the beauty of having a built-in image generation model inside of a coding agent like this, so you don't have to switch between different apps to get the result that you want. So, what it's doing now is actually it's going to use the image generation skill for this, and it's going to come up with five different design options for me. All right, so that is done. It's got five different options here, so let's run through all of these, right? So, I think this one looks pretty good. It's quite clean. It looks a lot like Calendly. But just look at the details. I mean, all the UI elements are here, how the buttons look. I think it just looks really professional. Let's take a look at the second one. I like this one as well. I mean, this is really, really well designed. Uh let's take a look at the some of the ones here. Uh I think this one's okay. Um let's move on to this one. Well, I think this one looks really nice, actually, with the dark UI. And the last one here, I feel like this is just a blend of like number one and number two. It's got green and red here, which I don't really like cuz I just want to have like one theme, and I don't think the color works here. By the way, if you like this ideas, you're only seeing the tip of the iceberg cuz I'm always digging into new business ideas, especially things that you can build using AI that makes money. But honestly, I can't turn every single idea into a YouTube video. So, a lot of the best ideas don't make it to the channel, but they go straight to my newsletter instead. This is where I track and share fresh business ideas, ideas that are already making people money. So, if you want to be the first to know about these before they go mainstream, join my free newsletter. It's completely free, link down below. Now, let's say you're happy with this design and you want to start building the website. Now, if you notice, this is just an image, so nothing is clickable now. So, you want to start creating or building the front end, and we're going to use Cloud Design for that. And when I say building front end, it simply means that I want all these buttons to be clickable, and I want to be able to navigate through all these pages. Basically, make everything come to life. done, we're going to bring it over back to ChatGPT Codex to build out the functionality. So, what you want to do now is you want to just download this image to your desktop and just upload it to Cloud Design. Now, if you've never used Cloud Design before, it's actually very simple. So, you want to go to cloud.ai. So, this is not the desktop app. It lives on the browser. So, you just want to log in to your account, and you're going to need at least the pro plan to be able to access Cloud Design. And when you're logged in, you want to look to the left, and you'll see a tab called Design. And you simply want to click on this, and it will open a page like this. And then you want to just name your project Meet Lee. And then you want to choose high fidelity and hit create. And you want to bring over the screenshot of the UI that you generated from Codex. So, I'll just drag over that file here and drop it like so. And if you look here, obviously, I don't want every single thing here. So, I just want basic functionality, and I'm just going to go back here and I'm going to tell Claude the exact features that I want and what I don't want. So, here is the prompt that I have. So, basically, I'm just telling it to create two pages and I want to give it more context like this is a calendar booking app similar to Calendly, but I have the design that I want, which is this one. And for the booking page on the left, I want the logo, the profile. So, all of these is just me dictating to Claude what pages I want and how things should navigate, but still using this as the design reference, if that makes sense. So, that's all you need and you can just hit send. Now, it will analyze what you want and it will just build this out for you in just a few minutes. All right, so, in just a couple minutes, it's done. That took about 4 to 5 minutes. So, you'll see all the HTML files here and all the assets are here as well in these folders. And let's start with the booking page. So, this is what it's able to create. Well, that just looks amazing. It followed all the design instructions exactly and all of these are now clickable, right? You can see that I'm able to click on the dates here and I can also choose the time zone. And then down here, there's a form where people can just write their name and their email. And then you can confirm booking. Of course, this is not functional right now, but the button animates when you hover on it. And then you can see all of this is also very, very well designed. And obviously, this will populate when you actually upload a photo. Now, let's look at the actual dashboard for the host. All right. So, very impressive. Everything is really, really organized and you can see the upcoming bookings. Of course, all of these are dummy data, but these are how the buttons will animate when you click on it. And you can see the availability here. You can see the event types. And then when you actually go to the pages, it has created all the pages here. You can create new events here. And then if you go to bookings, you can see all the bookings that has been made, availability. And let's see if these toggles actually work. Yeah, so they work. And then you can see the uh the time selection here, and then all this drops out. They actually work, right? I wouldn't change a thing here. I think it looks really, really good. Now, the nice thing about Cloud Design is that you can actually make changes here before you bring it over to Codex. For example, if I want to change certain things here, I can just click edit. Maybe I don't like the background. I want to change it to another color, I can do that here. I can change the font, um things like that. So, it's very customizable. So, I'll just take design, and I just want to bring it over to Codex, and I want to build out the functionality, the back end of it. What you can do now is you can actually hit share, and then you want to download this project as zip, and it will download all these files that you see here to your computer, and you want to put it in that folder that Codex has access to. Quick break from our sponsor, Build Your Store AI. So, if you have a product idea, something that you want to sell, this AI tool basically builds your website from scratch in just minutes. So, if you ever want to launch a product, or you want to test an idea really quickly, this removes all the friction. The website is powered by Shopify, basically the best platform for selling products online. So, let me quickly show you how this works. So, if you click on the link I've got below, you'll land on this page. You can sign up for a free account, and you want to click on choose your store niche, and in this case, let's use pets, and just follow the instructions here, and just in a few seconds, you get this beautiful website done in just seconds with all these products. These are all really beautiful, and everything is fully customizable to your brand. And you also get a Shopify store with a website. And what's nice about this is that you'll really get good pricing if you sign up this way, just a dollar for 3 months. Now, what's even better is that if you also install this plugin called AutoDS, you can immediately add products to your store and have the factory automatically fulfill and ship your orders to your customers, so you never have to touch the products, which saves you a lot of time from doing everything manually. So, if I'm selling pet toys, for example, I can just type in pet toys here in the marketplace. Let's say I like this one. I can just click on import and it would automatically appear on your Shopify store. And if you just check your website, it automatically pulls all the images, the product name, and also the description. Now, they've also got a sourcing request feature where the AutoDS team will work with you to source products from the best factories with the best pricing and the fastest shipping times. So, if you guys want to give it a try, build your store today with AI using my link below. Thanks again Build Your Store for sponsoring this video. Now, back to building our app. All right, so I just saved that folder here that I downloaded from Claude. I called it Meetly Design. And these are all the files that were created from Claude Design, right? Now, I'm going to go back to CodeX here and I'm going to say in the Meetly app folder, there's a subfolder called Meetly Design. I designed the full UI. Please study it and tell me if you have everything you need to build out the functionality. And I'm going to hit go. And now it's going to analyze all the files that you just created on Claude and it's going to tell you whether it has everything it needs to start building the back end. All right, so it looks like it has everything. It has enough to proceed. No missing design files from what I can see. Ready to go, right? So, you can prompt it, "Okay, build out the back end functionality. Make sure that every function works. And after you're done, I want you to use browser use to test all the functions." So, this is really really cool where you can ask the agent to actually test out all the functionality on the website before handing it over to you. So, let's hit go and we're going to wait a couple more minutes. All right, so it looks like that is done. So, that ran for about 4 minutes. So, not bad. And it was able to build all those pages out and it's living here on the local host. So, this just means that it's still living on your computer. It's not on the internet yet, but that's what we want cuz you we still want to make changes, right? So, you click on this and it will actually open the browser within CodeX. So, here you can see what it looks like. Now, you can immediately see that it has applied all the UI designs that we fed it. So, really happy with this, but I want to actually open this on my Chrome browser so we can see everything better. So I'm going to right click and open an external browser and they'll just open it on a browser like this so you can see the whole picture, right? Now, let's do a quick check here. I let's browse through the different pages here. Okay, so event types, discovery call. Okay, I can toggle on and off now. Um what if I want to create new event? Okay, there you go. So test event. See if this works, right? 45 minutes, create. And it's right here. Okay, it's here, right? So the functionality works and then we go to bookings. Okay, so we've got a couple of dummy data here. So let's say I want to join. Obviously this will go into Zoom, right? But let's say I want to cancel. See if that works. Okay, that works. But if you're doing this live, you do want that confirmation. Are you sure you want to cancel? I think that's better user experience. Availability. Okay, we've got some toggles here that actually works. So that is amazing. Integrations. All right, so integrations, this is what we're going to do next. So this is just a placeholder, right? It's not actually connected cuz we haven't connected it, but we're going to do that soon. All right, so let's check out the booking page. There you go. So I think it's also looks really, really good. Calendar works here. Okay. And then if I click this one, right? Perfect. And I can see the time zone. Obviously there are more time zones than this. I can ask it to fix it again. And then all of this works. And let's give this a test actually. So Jamie testing, jamie@gmail. Okay, I'm going to leave everything else blank, confirm booking. There you go. And then I'm going to go back to my dashboard and hit refresh. And see if that actually went in. Yep, there you go. Jamie test. So yeah, amazing for the first pass. So I want to go back to Codex and here's the thing that I wanted to show you earlier. So it actually did some testing of the booking in the back end, but I didn't capture it on video so I want to ask it to do that again and see if we can capture that. Use browser use to test uh dummy booking. And then let's see what happens. Okay, so it's reading browser skill. Now, it's actually using its own cursor here. You can see the cursor moving around and this is highlighted in blue. That means it's actually controlling the browser and it's going to do a test booking for us to see if everything works. So, I'm not touching the mouse now. It is actually doing everything by itself as you can see from the activity here. And this is really good if you're building some type of app. I think it's good that it's able to do this. And there you go. We got a confirmation and then it's probably checking whether it actually went through dummy booker here. Yeah, so confirmation that everything works from the agent. I love that. So, what's nice about having a browser here is the fact that you can actually annotate. So, you can click here on annotate. And then now you'll have a cursor where you can actually ask it to make some changes. So, let's say I want these numbers here to be green. And then I can say, "Make this green." And once you make a comment, it was going to show up here on the prompt and then you can just say implement changes. And it did change that color to green. Now, I didn't ask it to change anything else, so it did exactly what I wanted. And if I wanted to change the these other boxes, oh, I had to specify in the prompt. Now, I'm going to close this for now and I'm going to add the next feature that is really important, which is Google login, right? So, you want to allow people to login. So, I'm going to say, "I want to allow people to login via Google. Give me the steps to do this." And then I'm going to hit enter. Now, while that's working, I want to actually ask another agent to perform another task, which is to create a marketing video. Cuz if you have an app, you want a marketing video to promote your app, right? So, I'm going to go back to the sidebar here and I'm going to create another chat, which is to spin up another agent. Now, in order to create a video, you want to install a plugin called Remotion. So, you just want to click on plugins here and just type in Remotion here, and then you want to make sure that this is installed. Just click on it. And I already have this enabled here. So, if you don't, just toggle this on, and then you're good to go. You can go back to your chat here. So, you can say something like use @remotion here. And create a launch video to market this app, and you want to show off the booking page, how people can book, and also dashboard where hosts can manage bookings, blah blah blah. And I want you to animate the buttons. And just hit go, and it's going to tell you when it's done. And that's the beauty of working with Codex cuz you can spin up a couple of different agents working on many different things. So, you can build everything simultaneously. So, let me go back to the main chat. We want to start implementing the Google login. So, it's asking me to go to Google Cloud project, go go to this page, and set up an API, right? So, I'm just going to click on this. And I'm just going to create a new project in Google Cloud. So, this allows our app to connect to Google to allow for the Google login. So, I'm going to click here, and I'm going to hit new project. I'm going to call it Meetly app. And then no organization, and then just hit create. And I'm going to click here to get to that project. There you go. And then let's look at the second step, which is finding this OAuth screen here. So, just copy and paste this one and search for it. And then there you go. Click in here, and just go through the screen here. And then go back to Codex when you're done. Now, just select an email that you have just for support and hit next. Pick external here cuz you want it to be available for other people to test as well, and click next. And then you just want to enter your email again. Finish, continue, and then create. And you're done. You also want to create the client ID. Application type, I'm going to say web application, and then call it the name again, Meet Lee app. And then for authorized JavaScript origins, go back to Codex and it should give you this URL here. So, just copy and paste that URL. And then for redirect URL, I'm going to add this URL, which is also provided by Codex. And then just hit create. And that's it. So, I just gave that information to Codex and it's going to do everything for you in the back end. All right. So, looks like it's done. So, I'm going to test this out. So, if I go back to this booking page here, let me refresh the page actually, and then hit sign in. There you go. So, we've got the Google login right here. And it actually created this page, which is nice. So, continue to Google and let's see if this works. Pick one of my emails, hit continue. That's it. I'm in. So, that works. And now of course, you can implement Apple login, Microsoft login, or just the regular login. And you can do that by simply just asking Codex for the step-by-step. Now, the next feature I want to add is the ability to connect to a Google calendar cuz that's a primary feature of an app like this. So, I'll go back to Codex and I will just ask it to do that. And before we do that, it looks like the video is done. So, let's click on this. It's It's got the pulsating blue light here, which shows that it's done. Let's click this and then let's click on this link here and then it's got different assets here. Okay. So, let's just play this video. Wow. So, it did everything. So, it took the UI design that we created and it put everything in a video format uh clicking everything, of course. It is not perfect. So, I didn't give it a lot of prompting. I think at the first try, it's pretty good and it would have taken someone quite a long time to do this, right? Now, let's go back to the main chat here and I want to install the ability to connect to a Google calendar. So, I want the user to be able to connect to a Google Calendar. Please install the feature. All right, so it's asking me to enable something again, which is the Google Calendar API on the Google Cloud Console. So, I'm going to go back to that and then I'm just going to search for Calendar API and it should be here. There you go. And I'm just going to simply enable this. And then I have to go to OAuth consent screen, go to data access, and then add remove scopes, and then just going to copy both of these, put it down here, add to the table, update. And then you want to make sure you hit save. Now, let's see if this works. So, if I hit refresh here, I go to integrations, and then there you go. Google Calendar not connected, and there's a prompt to connect. So, I'm going to hit connect here and just log in to my account. And this is okay, hit continue, continue again, and then I'm going to select all of these and hit continue. And there you go, you're connected to the calendar. So, that works. Now, I'm going to do one more test, see if everything is working correctly. So, if I go to availability, um you can see that all of these are enabled. So, let's say I'm not available on Friday, so I'll just toggle this off and see if that populates on the front end. So, here is Friday's. Let me refresh. There you go, so it's off. So, it is working. Everything is connected nicely, and I'm very happy with the design. I did all of this in just 15-20 minutes, and I think this looks really, really good. Now, when you're happy with your app, the next thing you want to do is you want to install a database, right? Cuz what we have today here is a demo version, which lives on your local computer, but once you want to have it live, available for the public, you're going to need somewhere to store this user data here. So, for example, if someone creates an account and they're getting bookings, they're making changes to their account, you want all those changes to be safe somewhere, right? And that's where a database comes in. So, for this, I do recommend using Superbase. You just need to create a free account here and tell Codex to help you set this up as well. And you can accomplish this very easily with just prompting. And once that's done, you can also store your files to GitHub. And once you're done with this, you can connect it to Vercel to host the website for free. And you can connect it to your own domain. So I can't show you every single step here on how to do this, but this is a pretty common setup and it's very simple to do with just prompting the AI and it will guide you through every single step. And that is just the beauty with all of this, right? Cuz you don't need to know how the code works behind the scenes. You just have to ask it to guide you through the process and you can ask it to build it for you in plain English, right? That's the beauty of live coding. And by the way, tell me in the comments guys, what other apps do you want me to build next? You know, I read all the comments and if it's a great idea that everybody can get value from, I'll definitely do a video on it. Now if you want to see other app ideas, I just recently made a video on how I rebuilt an iOS app that's making $400,000 a month completely from scratch using Cloud Code. So if you want to watch that video, click here and I will see you there.