Free developer tools
Small tools we use while teaching: format and check JSON and SQL, test a regular expression, encode and decode Base64, read a JWT, generate UUIDs, explain cron schedules, change text between UPPER, Title and camelCase, count words and reading time, compare two texts line by line, make URL slugs, and practise typing real code. Every tool runs in your browser, so nothing you paste leaves your device.
JSON Formatter & Validator
Beautify, minify and validate JSON. Errors show the line, the column and why.
Open toolRegex Tester
Test a regular expression live, see matches and groups, and copy common patterns.
Open toolTyping Speed Test for Programmers
Type real code snippets, get WPM and accuracy, and learn finger placement for symbols.
Open toolSQL Formatter
Beautify or minify SQL queries for MySQL and PostgreSQL, with upper-case keywords.
Open toolBase64 Encoder & Decoder
Encode text or files to Base64 and decode it back, with UTF-8, URL-safe and data URL support.
Open toolJWT Decoder
Read a JWT header, payload and expiry in plain English. Decode only; the token never leaves your browser.
Open toolUUID Generator
Generate random v4 UUIDs, one or 1,000 at a time, in any format. Check a UUID's version too.
Open toolCron Expression Generator
Build or paste a cron expression, read it in plain English and see the next 5 run times.
Open toolCase Converter
Switch text to UPPER, lower, Title or Sentence case, or camelCase, snake_case and kebab-case.
Open toolWord Counter
Count words, characters, sentences and paragraphs live, with reading and speaking time.
Open toolText Compare Tool
Compare two texts or code files line by line and see what was added, removed or changed.
Open toolSlug Generator
Turn titles into clean URL slugs: lower case, hyphens, no accents, with a length limit.
Open toolWhy these tools
- They are free, with no sign-up, ads in the tool or usage limits.
- They work offline once the page has loaded, because all the work happens in JavaScript on your device.
- They are safe for real data. Nothing is sent to a server and nothing is saved, so you can paste an API response or a production query.