Frequently Asked Questions

Is my code sent to a server?

No, not for inline languages. HTML, CSS, JavaScript, TypeScript, the supported frameworks, Python, PHP, SQL and every other in-browser language run locally on your device and are never uploaded. Only turning on external previews sends Dart, Flutter or Angular code to DartPad, Zapp or StackBlitz to compile.

Can I save my work?

Your code is preserved in the URL when you use Share - bookmark or re-share that link to come back to it later. There is no account-based save system; this is intentional, to keep UniPreview login-free. Installing it as a PWA also lets you keep working offline in the same browser.

Why do Dart, Flutter, Angular and XAML behave differently from the other languages?

Dart, Flutter and Angular need a full compiler that cannot run in a plain browser frame. UniPreview shows the code with syntax highlighting, and once you opt in to external previews in Settings, a button to run it on DartPad, Zapp or StackBlitz. XAML is grouped with them and shown with syntax highlighting. This is intentional routing to the right renderer, not a limitation.

Does UniPreview support mobile devices?

Yes. UniPreview works in modern mobile browsers, and its device preview mode is built specifically to test how a layout renders at different screen sizes.

Is UniPreview really free?

Yes. UniPreview is free to use with no account, no paywalled features and no usage limits.

What browsers are supported?

UniPreview works in modern browsers such as Chrome, Firefox, Safari and Edge.

Can I upload a file instead of pasting code?

Yes - use "Upload file" / "Open file" in the editor to load code from your device instead of pasting it.

Is there a maximum code length?

There is no hard limit on what you can edit and preview, but UniPreview recommends keeping individual files under about 500KB for the best performance; very large files may be blocked from preview, and large projects are better shared as a link than as a QR code.