Free tools for developers
Format and convert data, test a regex, decode a token and check a domain. The tools run in your browser, so pasted data stays on your machine.
Data formats
Pretty-print and validate JSON, convert between JSON, CSV, YAML, XML and Excel, and generate TypeScript types from a sample.
- JSON FormatterPretty-print, validate and minify JSON.
- JSON to CSVConvert JSON arrays to CSV for Excel or Google Sheets, with nested fields flattened and the delimiter you choose.
- CSV to JSONConvert CSV or pasted spreadsheet data to JSON, with headers, types and quoted fields handled correctly.
- YAML to JSONConvert YAML to JSON and JSON to YAML in your browser, with clear errors by line and column.
- XML to JSON ConverterConvert XML to JSON and JSON to XML with your choice of attributes, arrays and namespaces, and format or validate XML.
- JSON to TypeScriptGenerate TypeScript interfaces or type aliases from JSON, with nested types, optional keys, unions and null handling.
- Excel to JSONTurn an Excel sheet into JSON, with the header row as keys and numbers, true or false and dates kept as types.
- JSON to ExcelConvert a JSON array to an Excel .xlsx file with nested objects as columns and numbers and booleans kept.
Encoding, hashes and tokens
Base64 and URL encoding, SHA hashes and HMAC, JWTs to decode or sign, UUIDs, strong passwords and one-time 2FA codes.
- Base64 Encode and DecodeEncode text or files to Base64 and decode it back, with proper UTF-8.
- URL Encode and DecodePercent-encode or decode URLs and query strings, see every parameter, and spot double encoding.
- Hash GeneratorSHA-256, SHA-1, SHA-512 and MD5 hashes of text or files, computed in your browser, plus HMAC and checksum compare.
- JWT DecoderDecode a JSON Web Token, check its expiry and verify the signature, locally.
- JWT GeneratorCreate and sign a JSON Web Token with HS256, HS384 or HS512, with iat, nbf and exp helpers.
- UUID GeneratorGenerate UUID v4 and v7 in bulk, with or without dashes, and validate UUIDs.
- Password GeneratorStrong random passwords, generated locally and never stored.
- 2FA Code GeneratorGet TOTP or HOTP codes from a secret key or otpauth link, or create a new secret with a QR code.
Code helpers
Test regular expressions, format SQL and HTML, minify CSS and JavaScript, build cron schedules and convert timestamps and number bases.
- Regex TesterTest JavaScript regular expressions live with matches, groups, replace and an explanation.
- SQL FormatterFormat and beautify SQL queries for MySQL, PostgreSQL, SQL Server, SQLite and more, with indent and keyword case options.
- HTML FormatterBeautify messy HTML with clean indentation or minify it, with pre and script contents kept and unclosed tags listed.
- CSS and JS MinifierMinify CSS and JavaScript in your browser to make files smaller, with the size saved shown.
- Cron Expression BuilderBuild and explain cron expressions in plain English and see the next run times in your time zone.
- Chmod CalculatorTurn Linux file permissions into chmod numbers and back, like 755 or rwxr-xr-x, with each bit explained.
- Unix Timestamp ConverterConvert Unix timestamps to dates and back, in seconds or milliseconds.
- Number Base ConverterConvert numbers between binary, decimal, hexadecimal and octal or any base from 2 to 36.
Network and web
Split a subnet, look up DNS records, read HTTP headers and certificates, and parse a user agent string.
- Subnet CalculatorNetwork, broadcast, host range and mask for any IPv4 CIDR, plus IPv6 prefixes and splitting a network into subnets.
- DNS LookupAll DNS records of a domain: A, AAAA, MX, TXT, NS, CNAME, SOA and CAA, with SPF and DMARC checks.
- HTTP Header CheckerFollow every redirect of a URL, see each status code and grade its security headers.
- SSL CheckerCheck an SSL certificate: issuer, expiry date, days left, domain names and the chain.
- User Agent ParserRead a user agent string as browser, engine, operating system and device, with your own browser shown first.
- CSS Clamp GeneratorFluid font sizes and spacing with clamp(): set min and max size and viewport, copy the CSS and check zoom.
- PX to REM ConverterConvert px to rem and rem to px for any root font size, with a table you can copy as CSS.
Free apps and resources, checked by hand
All free lists- Free Code Editors and IDEs15 editors, each checked on the official page
- Free AI Coding Assistants9 assistants, each checked on the official page
- Free Sites to Learn to Code11 sites, each checked on the official page
- Free Password Managers10 managers, each checked on the official page
- Free Website Hosting15 hosts, each checked on the official page
- Free Web Analytics Tools14 tools, each checked on the official page
- Open-Source Alternatives to Popular Software20 programs, each checked on the official page
Guides
All guides- JWT vs Session Cookies: Where the Login State LivesSessions keep state on the server and hand out an ID; JWTs put the state in a signed token. How each travels, is revoked and leaks, and when to use which.
- How to Check a Suspicious Link Before You Click ItRead the real domain, expand shortened links without opening them, and check who owns a site and what its certificate says, with the FTC and CISA signs.
- Hashing vs Encryption vs Encoding: What Each One DoesEncoding rewrites data and anyone can undo it, hashing makes a fixed fingerprint nobody can undo, encryption hides data for the key holder. Real examples.
- JSON vs YAML vs CSV: Which Format for Which JobJSON for machines, YAML for files people edit, CSV for flat tables. The same records in all three, what each spec allows, and the traps in each.
- Technical SEO Checklist for a New WebsiteThirteen launch checks, each with Google's rule behind it and the tool that runs it: crawling, sitemaps, robots.txt, noindex, canonicals, mobile.
- Two-Factor Authentication Methods Compared: Which to Turn OnPasskeys, security keys, app codes, push, SMS, email and backup codes, ranked by what CISA and NIST say about phishing resistance.
Only the network tools ask our server, because a browser cannot query DNS or read another site's headers by itself. Everything else, including the JWT and hash tools, runs in your browser.