# HTML Online Viewer

> Write and preview HTML, CSS and JavaScript live in a sandboxed browser IDE, with device simulation, console and ZIP export. Free, no sign-up.

- URL: https://farvixo.com/tools/developer/html-viewer
- Category: Developer Tools (https://farvixo.com/tools/developer)
- Price: Free
- Last reviewed: 7 August 2026
- Publisher: Farvixo Technologies

## What is HTML Online Viewer?

HTML Online Viewer is a free developer utility from Farvixo that lets you advanced in-browser IDE — live HTML/CSS/JS editor, sandboxed preview, device simulation, console, AI fix/improve/generate & ZIP export. Your input is processed locally in the browser — nothing is sent to a server, which matters when the payload is a token, a config file or production data. Free, unlimited, no sign-up.

## Specifications

| Property | Value |
| --- | --- |
| Tool | HTML Online Viewer — Developer Tools |
| Purpose | Advanced in-browser IDE — live HTML/CSS/JS editor, sandboxed preview, device simulation, console, AI fix/improve/generate & ZIP export |
| Input | Text or values you enter directly |
| Output | Processed output you can copy to the clipboard or download |
| Processing | In your browser — files are never uploaded to a server |
| Price | Free, unlimited, no account required |
| Limitations | Bounded by your device's memory and CPU rather than a server quota |

## How to use HTML Online Viewer

1. **Paste your code or data** — Paste your snippet into HTML Online Viewer. It stays on your device, which matters when you are handling tokens, config or production data.
2. **Run it** — HTML Online Viewer processes the input instantly and points at the exact line when something is malformed, so you can fix it rather than hunt for it.
3. **Copy the output** — Copy the result to your clipboard or download it. Free, unlimited and no sign-up.

## Use cases

- Inspecting or reformatting an API payload while debugging
- Decoding a token or encoded value without pasting it into an unknown website
- Generating test data or identifiers during development
- Validating a config file before it is committed or deployed

## Tips

- Because processing is local, it is safe to paste real credentials or production payloads here — nothing is transmitted or logged.
- When parsing fails, the reported line and column point at the first invalid token, which is usually just after the real mistake.
- Bookmark the tool page directly; it loads without an account and works offline once cached.

## Common problems

- **Parsing fails on valid-looking input** — Usually a trailing comma, a smart quote pasted from a document, or an unescaped backslash. Check the reported position first.
- **Output has unexpected whitespace or line endings** — The source used CRLF line endings or a non-breaking space. Normalise the input before processing.
- **Non-English characters come out wrong** — The input was not UTF-8. Re-save the source as UTF-8 and paste it again.

## FAQ

### Is the code sandboxed?

Yes. Your code runs in an isolated iframe with restricted permissions, so it cannot reach the rest of the page or your session. That is what makes it safe to paste and run a snippet you found somewhere.

### Is my code uploaded or saved on a server?

No. Everything runs in your browser, which means nothing is stored and nothing is transmitted — but also that closing the tab loses your work. Export the ZIP before you leave.

### Can I test how a page looks on mobile?

Yes. Device simulation resizes the preview to common phone and tablet viewports, which catches layout problems far faster than resizing a browser window by hand.

### Can I load external libraries?

Yes, via a CDN script tag as you would in any page. Bear in mind the sandbox blocks some cross-origin requests, so a library that needs privileged access may not behave exactly as it would on your own domain.

### Can I import an existing project?

Paste your HTML, CSS and JavaScript into their panels and it runs immediately. Export as a ZIP when you are done, since nothing is stored between sessions.

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- [CSS Gradient Generator](https://farvixo.com/tools/developer/gradient-generator): Design studio for gradients — AI prompt, image palette extraction, mesh/aurora/noise types, animation & 6 export formats
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- [URL Encoder & Decoder](https://farvixo.com/tools/developer/url-encoder-decoder): Encode and decode URL components
- [JWT Decoder](https://farvixo.com/tools/developer/jwt-decoder): Decode JWT header and payload instantly

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