Developer Tools tools

Encode, hash, format and validate code and data. Everything runs locally in your browser.

📖 New to developer tools? Read our Free Online Developer Tools: The Complete Guide to Encoding, Hashing, Formatting and Sysadmin Utilities for a full comparison of every tool below and which one to pick.

In-depth developer tools guides

How Client-Side File Processing Works (And Why It Is Private)
What really happens to a file you drop on a web page that never uploads it: the File handle, the WebAssembly codec, and what does cross the network.

7z Extractor Online
Extract a .7z archive right in your browser. See every file inside, then download files individually or all at once. Nothing is uploaded.
Number Base Converter
Convert numbers between binary, decimal, hex and octal, or turn text into UTF-8 bytes and back, entirely in your browser. Nothing is ever uploaded.
Base64 Decode
Decode Base64 back to text in your browser. Handles URL-safe characters, missing padding and line-wrapped input, with correct UTF-8 output.
Base64 Encode
Encode text to Base64 in your browser with correct UTF-8 handling for emoji and accents. Instant results, and nothing you paste ever leaves the page.
Bcrypt Hash Generator & Verifier
Generate a bcrypt password hash or verify a password against an existing hash, entirely in your browser. Passwords never leave your device.
File Checksum Verifier
Compute the MD5, SHA-1, SHA-256 or SHA-512 checksum of any file and compare it against a published hash. Streamed in your browser, nothing is uploaded.
Chmod Calculator
Convert Unix permissions between octal (755) and symbolic (rwxr-xr-x) notation, with a per-group breakdown and a ready chmod command, in your browser.
Color Blindness Simulator
Simulate protanopia, deuteranopia, tritanopia and achromatopsia on a pasted hex palette and on an uploaded image, side by side, free and in your browser.
Color Converter, HEX, RGB & HSL
Convert colors between HEX, RGB(A) and HSL(A) live, with a swatch preview, alpha support and one-click copy. Free, private, runs in your browser.
Nginx & .htaccess Config Generator
Build Nginx or Apache .htaccess rules for HTTPS and www redirects, security headers, gzip and caching, SPA routing and a custom 404 page. No round-trip.
WCAG Color Contrast Checker
Check a text and background color pair against WCAG AA and AAA. Live ratio, four pass/fail badges, a styled preview and the nearest passing colors.
Crontab Expression Generator
Build a crontab expression from dropdowns (every 5 minutes, hourly, daily, weekly, custom), with a plain-English explanation and the next 5 run times.
SSL CSR Generator
Generate a PKCS#10 certificate signing request and its matching private key in your browser. RSA 2048/4096 or ECDSA P-256, SHA-256, with SAN.
Convert CSV to JSON
Paste CSV, TSV or semicolon data and get a clean JSON array. Auto-detected delimiter, optional type inference, leading zeros kept as strings.
Convert CSV to SQL
Turn a CSV or Excel file into CREATE TABLE and INSERT statements for MySQL, PostgreSQL or SQLite. Runs in your browser tab, so the file is never uploaded.
CSV Viewer
Open a CSV or TSV file as a sortable, searchable table in your own browser tab. No spreadsheet app, no upload, and you can export the filtered rows.
Curl Command Converter
Paste a curl command and get the same request as JavaScript fetch, Python requests, Node axios, PHP cURL or PowerShell. Parsed in your own browser tab.
Text Diff Checker
Compare two blocks of text and see added, removed and changed lines or words instantly in your browser. Nothing you paste is ever uploaded.
Dockerfile Generator
Generate a production-ready Dockerfile, docker-compose.yml and .dockerignore for Node, Python, Go, PHP or a static site. Multi-stage, non-root, healthcheck.
Duplicate File Finder
Find duplicate files and photos in a folder by size and SHA-256 hash, see how much space they waste, and export a txt or csv report. Nothing is uploaded.
SPF, DKIM & DMARC Record Generator
Build correct SPF, DMARC and DKIM DNS TXT records from senders, alignment policy, reporting addresses and a pasted DKIM public key. No server round-trip.
Encrypt a File with a Password
Password-protect any file with real AES-256-GCM encryption in your own browser tab. No upload, no account, and no server ever sees the file.
Encrypt a Text Message with a Password
Encrypt a text message with a password into a compact Base64 block you can paste into email or chat, entirely in your browser; nothing is ever uploaded.
Compare Excel & CSV Files
Compare two spreadsheets and highlight added, removed and changed rows and cells. Match by key column or by position. Nothing is uploaded.
Convert Excel to JSON
Convert XLSX or XLS spreadsheets into clean, structured JSON directly in your browser using SheetJS. Nothing is ever uploaded.
Fake Data Generator
Build rows of fictional names, emails, phones, addresses, companies, UUIDs and dates, then copy them out as JSON, CSV or SQL INSERT statements.
File Type Identifier
Identify a file's true format from its magic-number signature, with the MIME type, the correct extension and a verdict on the name it currently has.
.gitignore Generator
Tick the languages, operating systems and editors your project uses and get one combined .gitignore, with duplicate rules dropped automatically.
HAR File Viewer
Open a DevTools HAR capture as a sortable, filterable request table with sizes, timings, a waterfall and full headers, read on your own machine.
Hex Viewer
Read any file as a classic hex dump with offsets, hex columns and an ASCII pane, plus byte search, range selection and file-signature detection.
HMAC Generator
Compute an HMAC signature from a message and a secret key in your browser, with SHA-256, SHA-1, SHA-512 or MD5, printed as both hex and Base64.
HTML Decode
Turn named and numeric HTML entities back into real characters. Known names decode, unknown ones and bare ampersands are returned untouched.
HTML Encode
Escape &, <, > and quote characters into HTML entities, with an optional numeric pass for every character above ASCII. Runs on your own device.
HTML Minifier & Beautifier
Shrink a page of HTML in your browser, or re-indent a minified one, with before and after byte counts plus a real gzip measurement. Nothing is uploaded.
HTML Table Generator
Build an HTML table visually, paste from Excel/Sheets, add or remove rows and columns, merge cells, pick a styling preset, then copy clean HTML.
htpasswd Generator
Build one username and hash line for an Apache or Nginx .htpasswd basic-auth file, in bcrypt or MD5-APR1, computed inside your own browser tab.
IBAN Validator
Check one IBAN or a whole pasted column against the ISO 13616 mod-97 checksum, the per-country length and the account structure, without an upload.
JavaScript Beautifier
Beautify and format JavaScript or TypeScript, including minified code, in your browser with Prettier. Adjust indent, quotes and semicolons. Nothing is uploaded.
JSON Diff: Compare Two JSON Documents
Compare two JSON documents by structure, not by line. Reordered keys report no change, and every real difference gets a path you can copy or export.
JSON Editor Online
Edit JSON as an expandable tree. Click a value to change it, rename keys, add or remove entries, and keep a raw text view in sync the whole time.
JSON Formatter & Validator
Pretty-print JSON with the indent width you pick, or strip it back to a single line. The text is parsed and rebuilt, so what returns is a normalized copy.
JSON Schema Validator
Check a JSON document against a JSON Schema with Ajv, on draft-07 or 2020-12, and get a numbered error list with a path for each one.
JSON to Code (Model Classes)
Paste JSON and get typed model classes in Python (dataclass or Pydantic), Go, Java, Kotlin, C# or Swift, with real naming and nullability rules.
Convert JSON to CSV
Convert a JSON array of objects into a downloadable CSV file, with nested objects flattened via dot notation. Nothing is ever uploaded.
Convert JSON to Excel
Convert a JSON array of objects into a downloadable Excel (.xlsx) spreadsheet, right in your browser. Nothing is ever uploaded.
JSON to HTML Table
Turn a JSON array into a styled HTML table. Nested keys flatten to dot notation, columns can be trimmed and reordered, then copy the markup or the table.
JSON to TypeScript
Paste JSON, get TypeScript interfaces instantly. Optional properties, nested & array-of-object types, null handling, interface or type-alias output.
JSON Tree Viewer
Open large JSON as a collapsible tree. Expand or collapse branches, search keys and values, and copy the exact accessor path to any value.
JSONPath Tester: Evaluate JSONPath Expressions Online
Type a JSONPath expression and watch every match highlight inside the document tree, with a cheatsheet, ready-made queries and copy or CSV export.
JWT Decoder
Split a JWT into its header, payload and time claims, with pretty-printed JSON and readable dates. Display only, and it runs on your own device.
JWT Generator
Build a real signed JWT from a header, payload and secret. HS256, HS384 and HS512, with exp and iat helpers, signed by Web Crypto on your device.
Server Log Analyzer
Analyze Nginx and Apache access logs in your browser. Top IPs, paths, status codes, a traffic chart, an error rate, live filters and CSV export.
MAC Address Vendor Lookup
Identify a device maker from its MAC address, normalize the format into four notations, and run a whole pasted list of addresses at once in your browser.
MD5 Hash Generator
Generate the MD5 hash of any text in your browser. An instant 32-character hex digest, computed locally, with nothing sent to a server.
Meta Tags Generator
Generate title, description, canonical, Open Graph and Twitter Card meta tags with live Google, Facebook, X and LinkedIn previews, free, in your browser.
CSS Minifier & Formatter
Minify CSS in your browser for a smaller stylesheet, or beautify it back to readable code, with before and after byte counts plus a real gzip measurement.
Passphrase Generator
Draw a diceware-style passphrase from the real 7,776-word EFF list, with the exact entropy in bits and four crack-time rows worked out for you.
Password Generator
Draw a random password from up to 88 characters using the browser's own crypto random source, with an honest entropy figure printed beside it.
Password Strength Checker
Paste a password to get a 0 to 4 score, the estimated number of guesses, four crack-time rows and the exact patterns that weakened it.
PGP Encrypt & Decrypt Tool
Generate a Curve25519 or RSA key pair, encrypt and decrypt messages and files, and clear-sign or verify, with OpenPGP.js running in your own tab.
Privacy Policy Generator
Answer a short questionnaire and get a privacy policy template in HTML, Markdown or plain text, with optional GDPR and CCPA sections. Not legal advice.
RAR Extractor Online
Open a .rar archive in your browser and download each file individually plus a zip of the lot, or just the zip when there are many. No upload, no install.
README Generator
Fill in a short form and get a clean README.md with working badges and a live preview. Sections you leave blank never appear. Your draft stays local.
Regex Tester & Builder
Test a regular expression against sample text in your browser, see every match, position and capture group instantly. Nothing ever leaves your device.
Robots.txt Generator & Tester
Build a robots.txt with presets for blocking AI crawlers, staging lockdown and WordPress, plus a tester for path/bot rules. Free, private, no upload.
Schema Markup Generator
Build valid JSON-LD structured data for seven schema types, with required fields checked and the output escaped so it cannot break your page.
SEO Title & Description Pixel Counter
Measure a title and meta description in pixels rather than characters, with a desktop or mobile estimate and the likely truncated display. Free, local.
SHA-1 Hash Generator
Produce the SHA-1 digest of any text as 40 lowercase hex characters, computed by your browser's own crypto. For legacy compatibility, not security.
SHA-256 Hash Generator
Turn any text into its SHA-256 digest, 64 lowercase hex characters, using your browser's own crypto implementation. Nothing is sent to a server.
SHA-512 Hash Generator
Compute a SHA-512 digest of any text, 128 lowercase hex characters, in your browser. Same SHA-2 family as SHA-256, twice the digest length.
SQL Formatter
Reformat a SQL query in your browser for Postgres, MySQL, SQLite, T-SQL or generic SQL, with an indent width from 2 to 8 spaces. Nothing is uploaded.
SSH Key Generator
Generate an Ed25519 or RSA 2048/4096 SSH key pair in your browser. OpenSSH public key line plus a PKCS#8 PEM private key. The key never leaves the tab.
SSL Certificate Decoder
Decode an X.509 certificate or a CSR in your browser. Subject, issuer, SAN list, validity with an expiry warning, key type and fingerprints. No upload.
IP Subnet Calculator
Paste an IPv4 address with a CIDR prefix or a dotted netmask and get the network, broadcast, wildcard mask, usable range and host count in your browser.
systemd Service Generator
Build a systemd .service unit with ExecStart, User, Restart, environment and dependencies, plus a matching .timer unit, live in your browser.
TAR.GZ / TGZ Extractor Online
Open a .tar.gz, .tgz, .tar or .gz in your browser and download the files inside individually or as one zip. Nothing is uploaded, nothing is installed.
TOTP Code Generator
Turn a Base32 secret or an otpauth URI into a live TOTP code with a countdown ring, for testing 2FA integrations. The secret never leaves the page.
Unzip Files Online
Extract a .zip in your browser and download the files inside individually, or take one bundled zip of the lot. Nothing is uploaded and nothing is installed.
URL Decode
Decode percent-encoded URLs and query strings back to readable text in your browser with decodeURIComponent or decodeURI. Nothing leaves your device.
URL Encode
Percent-encode text or a full URL right in your browser with encodeURIComponent or encodeURI. Instant results, and nothing ever leaves your device.
UTM Link Builder
Build campaign URLs with utm_source, medium, campaign, term and content, generate one per campaign name in bulk, and keep a local history. No account.
UUID Generator
Generate up to 1000 random version 4 UUIDs at once using your browser's own cryptographic generator. Nothing is uploaded and no library is involved.
Convert VCF to CSV
Turn a .vcf contacts export into a five column CSV with name, phones, emails, organization and address. Handles many contacts per file. No upload.
XML Formatter & Validator
Pretty-print or minify XML with an indent you choose, and get a real line and column for any syntax error. Nothing is uploaded and no library is needed.
XML to JSON Converter
Convert XML to JSON or JSON back to XML in your browser, choosing how attributes are represented, with a clear line and column for a parse error.
YAML to JSON Converter
Convert YAML to JSON (or JSON back to YAML) in your browser, supports multi-document manifests, anchors, and clear line-numbered parse errors.
Create ZIP Files Online
Combine any files into one ZIP archive in your browser with a real DEFLATE compression level you choose. Nothing is uploaded and no software is needed.

Developer Tools tools in action

Screenshot of the JSON Formatter & Validator tool with the sample input “{"site":"sysfenix","uploads":0,"categories":["im…”, Mode set to Format (pretty-print), Indent size (spaces, format mode only) set to 2 — JSON Formatter & Validator mid-process: the sample input “{"site":"sysfenix","uploads":0,"categories":["im…”, Mode set to Format (pretty-print), Indent size (spaces, format mode only) set to 2.

Screenshot of the Nginx & .htaccess Config Generator tool with Server type set to Nginx (nginx.conf server block), Force HTTPS (redirect all HTTP requests) set to on — Nginx & .htaccess Config Generator mid-process: Server type set to Nginx (nginx.conf server block), Force HTTPS (redirect all HTTP requests) set to on.