Actualización de una aplicación activa

Your app is live and people are using it. Now you want to improve it — fix a bug, add a feature, change the design. How do you update a running app without breaking it for users?

This lesson teaches the safe update loop: preview your changes first, ship them confidently, and roll back instantly if something goes wrong. With modern hosts and AI, this is smooth and low-stress.

Updating a deployed app follows a simple rhythm:

• Change your code locally (with AI's help).
• Test it on your laptop.
• Commit the change to Git.
• Push to GitHub.
• The host auto-deploys the new version live.

Because deploys are automatic, shipping an update is mostly about making good changes and saving them. The host handles the rest.

Here's a superpower: when you push to a branch (a separate copy of your code), Vercel and Netlify create a preview deployment — a temporary URL with your changes, separate from the live site.

This means you can see exactly how an update looks before real users do. If it looks good, you merge it to production. If not, no harm done — the live app was never touched.

A branch is a parallel version of your project where you can experiment safely. Your live app runs from the main branch; your work-in-progress lives on a feature branch.

Don't worry about memorizing Git commands — ask AI to handle branching for you.

The actual edit is the fun part. Describe what you want in Cursor or Claude Code, and let the AI write the change. Here's a tiny example of the kind of update you might ship — a function that flips a theme.

Before pushing, always run your app locally and click around. Catching a problem on your laptop is free; catching it in production affects real users.

Quick checklist before shipping:

• Does the new feature work?
• Did anything that worked before break?
• Are there errors in the browser console?

You can even ask AI: "Review this change — what might break?" It often spots edge cases you'd miss.

Happy with the preview? Promote it to live. Usually this means merging your branch into main, which triggers a production deploy.

On GitHub this is a Pull Request (PR) — a friendly review screen showing exactly what changed before you hit merge. AI can write the PR description and even review the diff for you.

• Open a PR from your branch to main.
• Review the changes (ask AI to summarize them).
• Merge — and your update goes live automatically.

Even careful builders ship a bad update sometimes. The good news: you can undo it in one click.

Vercel and Netlify keep every past deployment. If a new version misbehaves, open your deployments list, find the last working one, and promote it back to production ("rollback"). Your live app instantly returns to the good version.

This safety net is why shipping often feels stress-free — mistakes are reversible.

If users report a problem after an update, AI is your fastest path to a fix. Gather the details — what broke, any error messages, what you changed — and ask.

For real products with users, it's good practice to note what changed in each update — a simple changelog. It helps you remember and helps users know what's new.

You don't have to write it yourself. AI can generate a clean changelog from your recent commits.

The golden habit of confident builders: small, frequent updates beat big, rare ones.

• Small changes are easy to test and easy to roll back.
• If something breaks, you know exactly which tiny change caused it.
• Users get steady improvements instead of risky overhauls.

With preview deploys, instant rollbacks, and AI by your side, you can update your live app daily without fear. That's the modern way to ship.

You've learned to update a live app safely. One key idea to confirm.

You can now evolve your live app with confidence:

• Follow the loop: change → test → commit → push → auto-deploy.
• Use branches and preview deployments to see changes before users do.
• Test locally and let AI review what might break.
• If a deploy goes bad, roll back in one click.
• Ship small, ship often — and let AI handle PRs, debugging, and changelogs.

That completes Shipping & Deploying. Your app isn't just built — it's live, secure, and easy to improve. Go ship something!