Developer tools that keep your code and tokens local

Pasting a production JWT, an API response or a SQL query into a random website is a quiet security risk: you rarely know what the page does with it. Every tool on this page parses and formats your input with JavaScript in your own tab, so tokens, payloads and queries are never transmitted.

The tools cover the small, frequent jobs of day-to-day development — making data readable, converting between formats, decoding what an API sent back, and writing the one-line expressions (cron, regex, chmod) that are easy to get subtly wrong.

Data formats

Read, validate and convert structured data.

JSON Formatter & ValidatorValidate, beautify, or minify JSON, with the parse error surfaced when it fails.Local JSON ⇄ YAML ConverterConvert config files both ways with proper indentation — handy for Kubernetes and CI files.On-device CSV ⇄ JSON ConverterConvert in either direction with custom delimiters, quoted fields, and a file download.Local XML Formatter & ValidatorPretty-print or minify XML and pinpoint the first well-formedness error, with comments and CDATA preserved.Local JSON Schema ValidatorCheck JSON against a schema (drafts 2020-12, 2019-09, 07, 04) and list every error with its path, keyword and message.Local JSON Diff & CompareCompare two JSON documents semantically and list every added, removed and changed value by path, with a JSON Patch export.Local

Debug APIs and auth

Inspect what a request or token actually contains.

JWT DecoderDecode header, payload and expiry instantly — and verify HS256 signatures with your secret, locally.Local SSL Certificate DecoderRead a certificate or chain: subject, issuer, SANs, expiry, key size, extensions and fingerprints, locally.Local curl to Code ConverterPaste a curl command and get working JavaScript fetch, Node axios, Python requests, or Go source.Local HTTP Status Code LookupSearch every HTTP status code by number, class or keyword, with causes, fixes, RFC, caching and retry advice.Local Unix Timestamp ConverterRead the current epoch time and convert any timestamp to a readable local date.Local Text Diff CheckerCompare two versions line by line. Additions, removals, and collapsed unchanged regions.Local

Format and preview code

Make code and docs readable before you commit them.

SQL FormatterTurn one-line queries into readable SQL — MySQL, PostgreSQL, SQLite and T-SQL dialects.On-device HTML / CSS / JS BeautifierUnminify and re-indent markup, styles and scripts with js-beautify.On-device Markdown Editor & PreviewWrite Markdown and watch it render live — sanitized output you can copy as HTML.On-device

Expressions and generators

Get the fiddly syntax right the first time.

Regex TesterLive match highlighting with flags and capture groups, as you type.Local Cron Expression GeneratorBuild a schedule from fields or paste an expression to read it in plain English, with the next five run times.Local Chmod CalculatorClick permissions or type octal — get 755, rwxr-xr-x and the exact command both ways.Local Docker Run to Compose ConverterTurn docker run commands into a compose.yaml, with named volumes, networks and a list of flags that did not map.Local UUID GeneratorGenerate 1 to 1,000 random v4 UUIDs with the browser's crypto — copy or download the list.Local Htpasswd Generator & CheckerBuild .htpasswd files with bcrypt, APR1-MD5 or SHA-1 for Apache and Nginx, and check passwords against existing lines.On-device Bcrypt Hash Generator & VerifierHash a password with bcrypt at the cost you choose, check a password against a $2a$/$2b$/$2y$ hash, and see what each part means.On-device

More tools

Base64 Encoder / DecoderEncode text to Base64 or decode it back, including full Unicode input.Local URL Encoder / DecoderPercent-encode text for query strings, or decode an encoded URL back to readable form.Local HTML Entity Encoder / DecoderEscape text for safe HTML, or turn &-soup back into readable characters.Local Case ConverterOne input, ten cases at once — camelCase, snake_case, kebab-case, Title Case and more.Local File Hash & Checksum CheckerMD5, SHA-1, SHA-256, and SHA-512 for any file or text, plus a verifier for expected checksums.Local Image to Base64 ConverterImage to data URI, CSS, HTML or Markdown — and Base64 back to a downloadable image. Type detected from the bytes.Local

Good to know

Is it safe to paste secrets here?

For every tool on this page, yes — none of them make network requests with your input. You can confirm this in your browser's DevTools Network tab while using a tool.

Offline use

Once a tool has loaded, it keeps working without a connection — the work happens in your browser. Tools marked On-device download their open-source library the first time, so open them once while online.

Other categories

PDF Tools · Image Tools · Calculators · Network Tools · SEO Tools · Security Tools