> ## Documentation Index > Fetch the complete documentation index at: https://crevio.co/docs/llms.txt > Use this file to discover all available pages before exploring further. # Apps > Crevio doesn't just build websites -- describe a tool your business needs and it builds a real, working web app, then hosts it and changes it whenever you ask. Crevio builds more than marketing websites. Describe a tool your business needs and Crevio's AI builds you a real, working **web app** -- one that does something, not just one that shows something. Same as everywhere else in Crevio: you say what you want in plain words, and Crevio makes it. You never touch code, servers, or hosting. You talk to Crevio like you would a developer who never sleeps, and it builds, publishes, and looks after the app for you. ## Why you'd use this * **You need a tool, not just a page.** Something people can actually *use* -- book a slot, log in to an account, look something up, calculate a result. * **You are not technical.** No code, no databases to wire up, no hosting to buy. Crevio handles all of it. * **You want it to keep up with you.** As your business changes, you just ask Crevio to change the app -- no rebuilding from scratch. The golden rule of Crevio still applies: when in doubt, just ask. Describe what someone should be able to *do*, and Crevio will tell you what it can build and where it would split the work. ## What you can build Apps are open-ended, but here are common ones to spark ideas: | App | What it does | | ---------------------------- | -------------------------------------------------------------------------------------- | | **Booking tool** | Let customers see your availability and book a time, with confirmations and reminders. | | **Client portal** | A private, logged-in area where your customers view their orders, files, or progress. | | **Members area** | Gated content and a community space for paying members. | | **Directory** | A searchable, filterable list -- of listings, providers, resources, or anything else. | | **Calculator or quote tool** | Visitors enter a few details and get an instant price, estimate, or result. | | **Interactive dashboard** | A live view of the numbers that matter to you or your customers. | | **Simple internal tool** | A small app for you and your team to track or manage something day to day. | Not sure whether something counts as an "app"? Just describe what you want it to *do* -- "let people book a 30-minute call and pay a deposit" -- and Crevio figures out the rest. ## Ask Crevio to build it Open Crevio and explain the tool in your own words -- who uses it and what happens when they do. For example: *"Build me a booking app where clients pick a service, choose a time from my calendar, and pay a deposit up front."* Mention a style if you have one in mind, or leave it out and Crevio will match it to your business. Crevio assembles the real, working app -- the screens, the logic, and the data it needs to remember. You can watch the progress as it goes. When it's ready, Crevio shows you a preview. Click around and use it like a customer would. Nothing is final -- anything can be changed by asking. ## It's a real app, not a mockup The apps Crevio builds are the real thing: * **They remember data.** Bookings, submissions, accounts, and anything else your app collects are saved and stay put. * **They're hosted for you.** Crevio publishes the app and keeps it online -- no separate hosting to set up or pay for. * **They live on your web address.** Use the free `yourname.crevio.app` address or [connect your own custom domain](/docs/features/domains). * **You control who gets in.** Make an app public, limit it to signed-in customers, or keep it to your team while you build. See [choosing who can see your site](/docs/features/sites#choose-who-can-see-your-site). ## Your app's data is looked after Most apps remember things -- bookings, sign-ups, submissions, member profiles. That saved information is the part of your app you can least afford to lose, so Crevio treats it carefully. * **Crevio works on a practice copy, not your real data.** While it builds and tests a change, it works against a separate copy of your app's structure that holds none of your customers' information. Your live data is never the thing it experiments on. * **Changes are applied once, when you publish.** Crevio may reshape the practice copy a dozen times while it works. When you publish, it works out the difference and applies it to your live app in one clean step -- the false starts along the way never reach it. * **You're told what will change, in plain words.** Before it publishes, Crevio explains the change in language you can act on -- "adds a featured field to reviews," "removes the old signups table" -- so you can say no first. * **Anything that would destroy data stops and asks.** If a change would delete saved information, Crevio pauses and asks you to approve it, naming exactly what would go -- for example, the reviews table and all 1,284 entries in it. Nothing is deleted on your behalf without you saying yes. * **Undoing a change can undo the data change too.** If you roll back to an earlier version of your app, Crevio can rewind the saved information to the state that version was working with. You never have to think about any of this. Just ask -- *"What will this change do to my data?"* or *"Undo that last update and put my data back how it was."* Rolling the data back returns it to how it looked at the earlier version, which means anything saved since then is discarded. Crevio tells you before it does it -- if you're unsure, ask it to roll back only the app itself. ## Change anything by asking Once your app exists, improving it is just a conversation -- the same as with your website: * *"Add a cancellation option to the booking flow."* * *"Send me an email whenever someone signs up."* * *"Show the busiest days at the top of the dashboard."* * *"Let members edit their own profile."* Crevio makes the change and shows you the result. If it's not quite right, ask again. ## What it can't do Worth knowing before you plan around it. **It builds web apps, not phone apps.** What you get runs in a browser, on your own web address, and works on a phone screen. It isn't a native iOS or Android app you'd submit to an app store. **You don't write code in Crevio.** There's no code editor in the dashboard, by design — you change your app by describing the change. If you want to work on the code directly, you can: connect your own GitHub repository and Crevio builds and deploys from that instead, leaving the code somewhere you can read, edit and keep. Set it up in **Settings** → **Integrations**. **One version is live at a time.** Publishing replaces what's live. There's no staging site running alongside it. You do get a preview while a change is being made, and you can put an earlier version back at any time. **Big changes work better in pieces.** One clear change per request lands more reliably than one large one, and it's far easier for you to check. If you ask for something sprawling, expect Crevio to propose splitting it — that's it working properly, not stalling. **Some things need your approval.** A change that would delete saved information stops and asks first. That's deliberate and can't be switched off. ## If something goes wrong Tell Crevio what should happen instead, in plain words -- "when someone books, it should also ask for their phone number." Crevio adjusts the behavior. The clearer you are about what should happen, the closer the next version gets. Just ask Crevio to undo it or try another approach: *"That's not what I meant -- go back to how it worked and instead add the field to the second step."* If a published version is the problem, ask Crevio to go back to the previous one: *"Roll my app back to the version before today's update."* It puts the earlier version live again, and can rewind your saved data alongside it if the change affected that too. That prompt only appears when a change would delete saved information. Read what it names -- it tells you which information would go and how much of it. If that's what you intended, approve it. If it isn't, say no and tell Crevio what you actually wanted; safe changes like adding new fields never ask. Start with the outcome: what should a person be able to do, and what should happen when they do it? You can also ask Crevio for ideas -- *"What kind of app would help a cleaning business take bookings?"* -- and build from there. ## Related The same describe-it-and-it's-built approach, for your website. Put your app on a custom domain you own. Have your AI assistant do recurring work behind the scenes. The simple mental model behind everything Crevio builds.