LocalBench
Privacy-first developer tools that run entirely in your browser.
Privacy-first developer tools that run entirely in your browser.
LocalBench is a suite of everyday utilities — JSON formatting, text diffing, SQL beautifying, Base64 and URL encoding, JWT debugging, checksums, UUID generation, regex sandbox, subnet calculation, PDF tools, and more — built to run entirely as client-side JavaScript in your browser tab. No sign-up, no server round trips, and no data leaves your device.
JSON Formatter
Validate, format, and explore JSON
JSON Diff
Compare two JSON documents field by field, not line by line
JSON ↔ XML Converter
Convert JSON to XML or XML back to JSON
JSON ↔ CSV Converter
Convert a JSON array of objects to CSV, or CSV back to JSON
JSON to Types
Generate a TypeScript interface, Java class, or C# class from a JSON sample
Text Differ
Compare two blocks of text line by line
XML Formatter
Format, minify, and validate XML
HTML Formatter
Format or minify HTML, plus a common-issues check
CSS Beautifier
Format or minify CSS
SQL Beautifier
Reformat unruly SQL into readable queries
Base64 Encoder
Encode text or a file to Base64
Base64 Decoder
Decode Base64 to text, an image, or a file
URL Encoder
Percent-encode text or a full URL
URL Decoder
Decode a percent-encoded URL back to plain text
String Escaper
Escape and unescape strings for HTML, JavaScript, SQL, and CSV
JWT Debugger
Decode, inspect, and verify JSON Web Tokens
JWT Generator
Build and sign a test JSON Web Token
Hash Generator
Generate and verify MD5/SHA checksums for text or files
UUID / ULID Generator
Generate random UUID v4s or sortable ULIDs, in bulk
Case Converter
Convert identifiers between camelCase, snake_case, kebab-case, and more
Color Converter
Convert between HEX, RGB, HSL, and OKLCH, plus a WCAG contrast checker
Timestamp Converter
Convert between Unix epoch time and human-readable dates
QR Code Generator
Generate QR codes with a logo, for text, URLs, Wi-Fi, and contact cards
Image Compressor
Shrink a photo or screenshot by re-encoding it as JPEG, WebP, or PNG
RegEx Sandbox
Test regex patterns and see them explained plain-English
Cron Explainer
Decode a cron expression into plain English and upcoming run times
CIDR / Subnet Calculator
Calculate network/broadcast addresses, host range, and mask from a CIDR block
PDF Merge
Combine multiple PDFs into one, in any order
PDF Splitter
Extract specific pages from a PDF, or split it into separate files
PDF Page Organizer
Rotate, reorder, and delete pages in a PDF
PDF to Images
Export PDF pages as PNG or JPEG images
PDF Compressor
Shrink a PDF by recompressing its embedded images
HTTP Status Code Reference
Search every HTTP status code with a plain-English explanation
AI Tools Directory
Search a curated directory of developer-focused AI tools
Why LocalBench?
API responses, tokens, database queries, and private documents often carry sensitive data you shouldn't paste into a remote server. LocalBench runs everything directly in your browser tab.
Privacy by design
Every computation happens on your machine. There is no backend server receiving your inputs, so there is nothing to log, intercept, or leak.
Instant and free
No account creation, no usage quotas, and no network latency. Open a tool and your result appears immediately as you type.
Works offline
Once a tool loads, it continues functioning with zero internet connection — reliable for working on planes or restricted corporate networks.
Frequently Asked Questions
What does "runs entirely in your browser" actually mean?
Every tool's computation — parsing JSON, hashing a file, signing a JWT, rebuilding a PDF — is plain JavaScript executing in your own browser tab, using Web APIs like the DOM parser, Web Crypto, and Canvas. There is no backend and no API route: nothing you paste, upload, or type is ever transmitted anywhere, including to LocalBench's own servers. You can confirm this yourself by opening your browser's Network tab while using any tool.
Is LocalBench really free, and is there a catch?
Yes — every tool is free with no account, no usage limits, and no feature paywall. The site may show ads to cover hosting costs; there's no other catch, no data collection tied to what you paste into a tool, and no upsell path buried behind a tool's core functionality.
Do the tools work offline?
Once a tool's page has loaded, yes — since everything runs as JavaScript already in your browser rather than round-tripping to a server, most tools keep working with no network connection at all. Loading a page for the first time still needs a connection, the same as any website.
Why would client-side tools be better than a typical online converter?
Most "paste your JSON/JWT/file here" sites upload what you paste to a server to process it — which means a secret, an internal API response, or a customer record now exists, even briefly, on infrastructure you don't control and can't audit. Client-side tools skip that step entirely: the computation happens on your device, so there's nothing to upload and nothing to leak.
Do I need to install anything or create an account?
No — every tool is a regular web page. There's no browser extension, no desktop app, and no sign-up form; open a tool's URL and it's ready to use immediately.
Which browsers are supported?
Any current version of Chrome, Firefox, Safari, or Edge. Tools rely on standard, widely supported Web APIs (DOM parsing, Web Crypto, Canvas), so there's no special plugin or bleeding-edge browser feature required.