Client-side tools — nothing you type leaves your browser
Free online developer tools that run in your browser.
Format JSON, test regex, encode text, convert timestamps, generate UUIDs, and more — without uploading your data.
Find a tool
Search the real catalog, then open a tool or browse every category.
A local browser runtime
Every tool runs in this page. These are the guarantees the test suite enforces.
- Runs locally in your browserAlmost every tool is client-side code; the few server-backed lookups are labelled Server-side on their page.
- No upload requiredBrowser tools never upload input; server lookups send only the validated target and do not store it.
- No account neededThere is no sign-up, login or account affordance anywhere.
Popular tools
Editorial selection: measured usage is not yet sufficient to rank this honestly (no usage figures are shown).
JSON Formatter
/tools/json-formatter/Format and validate JSON while preserving large integers.
JSON Validator
/tools/json-validator/Check whether a document is valid JSON and report the first syntax error with its position.
Base64 Encoder / Decoder
/tools/base64-encoder/Encode UTF-8 text to Base64 or decode Base64 back to UTF-8 text.
URL Encoder / Decoder
/tools/url-encoder/Percent-encode or decode URL text, for whole URLs or single components.
Tool categories
Latest guides
Working with CSV and Delimited Data
How to view, convert, profile and merge CSV, TSV and PSV data locally without uploading a file.
Working with PDFs in the Browser
How to split, merge, inspect and edit PDF pages locally without uploading a private document.
Working with SQL Safely in the Browser
How to format, validate, safety-check and split SQL locally without connecting to a database.
Why trust this site
- Runs locally in your browserTool code runs in this page; no server computes your input.
- No upload requiredTool input is never sent anywhere; the privacy scan enforces it.
- Server-side lookupServer-backed lookups send only the validated target to the platform API; the page labels them Server-side.
- Query not stored or loggedLookup queries are used for the request only; the RULE-029 tests prove they are not stored or logged.
- Sources providedFactual tool and guide claims cite a named primary source.
- Reviewed contentEvery published item carries an author and is reviewed first.
- Clear limitationsEvery tool and guide states where it stops being reliable.
About & editorial principles
Gampangin publishes small, focused developer tools and the documentation that makes them trustworthy. Every tool runs in the browser, every factual claim links to a source, and every page is reviewed before publication.