Drop in the raw data
Paste a payload, markup snippet, stylesheet, or text block directly into the matching tool.
100% in-browser developer utilities
Use developer tools on real data without sending it anywhere.
Format JSON, preview HTML, inspect XML, clean JavaScript, convert CSS units, and compare text in one fast workspace built for privacy-first debugging.
- Source data stays in browser memory
- No request queue, no upload step, no server wait
- Keyboard shortcuts across the full suite
100% local processing
Useful for payloads, keys, snippets, and internal markup you do not want routed through a third-party backend.
One suite, seven workflows
Jump from JSON cleanup to HTML testing, CSS formatting, Markdown preview, or text encoding without changing products.
Made for scanning
Short actions, obvious entry points, and direct tool labels instead of a marketing-heavy homepage.
Tool suite
Start from the task you need to finish.
Each tool is focused, fast, and tuned for common developer cleanup jobs.
JSON Viewer
Format, minify, unescape, inspect in tree view, and convert JSON to YAML.
HTML Sandbox
Preview markup live, test responsive behavior, and open a clean browser tab render.
XML Viewer
Validate structure, pretty-print documents, minify payloads, and convert XML to JSON.
JavaScript Tools
Beautify scripts, minify output, run syntax checks, and test snippets in a sandbox.
CSS Viewer
Format stylesheets, compress CSS, convert px to rem, and review extracted color values.
Text Utilities
Diff text, encode or decode Base64 and URLs, and clean escaped strings quickly.
Base64 Tool
Encode and decode UTF-8 text, emoji, and Data URIs to and from standard or URL-safe Base64.
JWT Decoder
Inspect the header, payload, and claims of any JSON Web Token with expiry checks.
Markdown Previewer
Write Markdown and see a live HTML preview instantly, then copy or export the rendered HTML.
How it works
A shorter path from raw input to usable output.
Paste your input, run the tool, and copy the clean output back to your code.
Run one obvious action
Format, minify, preview, convert, diff, or decode with clear controls and shortcut support.
Copy out the result
Take the cleaned output back to your editor, API client, design handoff, or debugging session.
Product reasons
Why developers choose client-side utilities.
Speed is useful, but the bigger win is keeping private material out of server logs and upload pipelines.
Better for sensitive payloads
Paste tokens, config fragments, API responses, or internal markup without routing them through a formatter service.
Faster debugging loops
When there is no upload step, you can inspect, fix, and copy results back out immediately.
Consistent tool language
One interface model across JSON, HTML, XML, JavaScript, CSS, and text utilities reduces learning cost.
Built for repetition
Hotkeys and direct actions make the suite practical for day-to-day cleanup instead of a one-off marketing demo.
What "private" means here
We built OnlineViewer Dev because pasting production tokens or client data into third-party formatting services is a security liability. Everything runs right inside your browser.
- JSON payloads stay local to your session
- HTML preview runs in your browser, not a remote render service
- Formatting and conversion happen without a backend processing queue
Learn the workflows behind the tools.
Format JSON and convert it to YAML
Understand the JSON cleanup flow and when YAML export helps.
Preview HTML and test responsive layouts
Use the HTML sandbox for fast browser-side iteration.
Convert XML into structured JSON
See how the XML tool supports validation and transformation.
Preview Markdown and convert it to HTML
Learn the Markdown live preview and MD-to-HTML workflow.
FAQ
Common questions before you start.
Everything you need to know about how your data is handled.
Is my code or data uploaded to any server?
No. Formatting, parsing, and minification happen entirely inside your web browser. Your code and payloads are never sent over the network.
Which tool should I open first?
Start with the data type you already have. JSON for payload inspection, HTML for live rendering, Markdown for docs preview, XML for document cleanup, JavaScript or CSS for formatting, and Text for diffs or encoders.
Can I test responsive HTML layouts here?
Yes. You can test your HTML live and toggle mobile, tablet, or desktop viewports in real time.
Ready to use
Open a tool and start with the data you already have.
No signup, no tracking, and no wait time. Select a tool, paste your data, and get to work.