Developer Tools

.env File Checker

Lint a .env file for syntax errors, duplicates and weak secrets.

.htaccess Generator

Build an Apache .htaccess from toggles for HTTPS, caching, headers and more.

AES Key Generator

Random AES-128, 192 or 256-bit keys in hex, Base64 or JWK.

AI Token Counter

Count GPT tokens in a prompt or document with o200k_base, in your browser.

Alt Text Helper

Compose the right alt attribute for decorative, informative and functional images.

API Key Generator

Random prefixed API keys with an optional checksum, like GitHub tokens.

ARIA Attribute Builder

Generate the right role and aria attributes for any common widget.

ARIA Label Generator

Write clear aria-label text for icon buttons, links and unlabelled inputs.

ASCII Table

All 128 ASCII codes in decimal, hex, octal and binary.

Audio Embed Code Generator

Build an HTML5 audio tag with the right MIME types and options.

Audio Sprite Maker

Pack sound effects into one audio sprite with a howler.js JSON map.

Audio To Base64

Turn a short audio clip into a base64 data URI.

Backup Code Generator

Random two-factor recovery codes, grouped for easy reading.

Base Converter

Convert numbers between binary, octal, decimal and hex.

Base32, Base58 And Base85 Encoder

Encode and decode Base32, Base58, Ascii85 and Z85.

Base64 Encoder / Decoder

Encode and decode Base64, standard or URL-safe.

Basic Auth Header Generator

Build or decode an HTTP Authorization Basic header.

Bcrypt Cost Benchmark

Time bcrypt cost factors and pick one that fits your login budget.

Bcrypt Generator

Generate and verify bcrypt password hashes.

Bearer Token Decoder

Decode an Authorization header and find out what kind of token it is.

Browser Detector

See your browser, OS, screen and supported features at a glance.

Cache-Control Header Builder

Build a Cache-Control header and see exactly how browsers and CDNs will treat it.

Canonical URL Generator

Normalise URLs to their canonical form and generate rel=canonical tags.

Certificate Chain Order Checker

Check your SSL certificate bundle is complete and in the right order.

Certificate Expiry Calculator

See days left and the renewal date for any PEM certificate.

Checksum Verifier

Check several files against a SHA256SUMS list, like sha256sum -c.

CHMOD Calculator

Convert Unix permissions between rwx, octal and symbolic.

Chmod Cheat Sheet

Permission digits, common modes and special bits on one page.

Code Line Counter

Count code, comment and blank lines in a source file.

Config Generator

Turn key = value lines into .env, JSON, YAML, TOML or INI files.

Context Window Calculator

Check whether a prompt, documents and reply fit a model's context window.

Cookie Parser

Break Set-Cookie and Cookie headers into readable attributes with warnings.

Core Web Vitals Calculator

Check whether your page passes Core Web Vitals and which metric to fix first.

CORS Tester

Test a URL for CORS headers or analyse pasted ones.

CRC32 Calculator

CRC-32, CRC-32C and Adler-32 checksums of text or hex bytes.

Cron Cheat Sheet

Crontab fields, operators and ready-made schedule expressions.

Cron Expression Builder

Build a cron schedule and see when it actually runs.

CSP Builder

Build a Content-Security-Policy header from per-directive source lists.

CSP Tester

Explain a CSP, flag weaknesses, and test whether a URL would load.

CSR Decoder

Decode a CSR, verify its signature and spot problems before submitting.

CSS Formatter

Expand minified CSS to one declaration per line, or minify it back.

CSS Nesting Converter

Nest flat CSS with & or flatten nested CSS back into plain rules.

CSS Selector Tester

Test a CSS selector against pasted HTML and list every matching element.

CSS Size Calculator

Measure a stylesheet's real transfer size and see whether it blocks first paint.

CSS Units Cheat Sheet

Every CSS unit, what it is relative to and when to use it.

CSS Validator

Find typos, missing semicolons and unknown properties in pasted CSS.

CSV / JSON Converter

Convert CSV to JSON and back, quoting handled properly.

CSV Column Extractor

Keep, drop and reorder columns in CSV data.

CSV Formatter

Align CSV into readable columns or swap delimiters and fix quoting.

CSV To Excel Converter

Convert CSV to an Excel workbook, or an Excel sheet to CSV.

CURL Converter

Turn a curl command into code in 24 languages.

CVE ID Validator

Check a list of CVE IDs for format errors and duplicates.

CVSS Calculator

Score a vulnerability with CVSS 3.1 from metrics or a vector.

DMARC Record Generator

Build a DMARC record with the right policy and report addresses.

DNS Lookup

Query any DNS record for a domain with TTLs and explanations.

EC Key Generator

Elliptic curve and Ed25519 key pairs as PEM or JWK.

Email DNS Record Checker

Check an SPF, DKIM or DMARC record before you publish it.

Email Validator

Check a list of email addresses for syntax errors and likely typos.

Embedding Cost Calculator

Estimate what it costs to embed documents and how much storage the vectors take.

Epoch Converter

Convert Unix timestamps to dates and back again.

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ER Diagram Maker

Type tables and relationships to draw a crow's foot ER diagram.

Factor Calculator

All the factors, factor pairs and prime factorisation of a number.

Factorial Calculator

Exact n factorial up to 5000!, with digits and trailing zeros.

File Hash Checker

Hash a file and check it against the published checksum.

File Size Converter

Convert any file or drive size into every decimal and binary unit at once.

File Type Identifier

Check a file's real type from its bytes and spot disguised programs.

Filename Generator

Safe, consistent file names from plain words, with dates and suffixes.

Firewall Rule Explainer

Explain iptables and ufw rules in plain English and flag risky ones.

Focus Indicator Generator

Build a visible, WCAG-friendly focus ring and copy the :focus-visible CSS.

GCF Calculator

Greatest common factor of two or more numbers, with every step.

GeoJSON Editor

View GeoJSON on a map, draw new features and download the file.

Git Cheat Sheet

Find the right git command and whether it is safe to run.

Git Secret Removal Guide

Step-by-step commands to purge a leaked secret from git history.

Gzip / Brotli Size Comparison

Compare what gzip and Brotli save on a real file.

Hash Generator

Generate MD5, SHA-1, SHA-256 and SHA-512 digests from text.

Hex Dump Viewer

View any file as hex and ASCII, with type detection and entropy.

HMAC-SHA256 Generator

Sign a message with HMAC-SHA256 and verify signatures.

Hostname / Device Name Generator

Hostnames like kestrel, basalt and web-prod-03 for servers, laptops and home lab boxes.

HOTP Generator

Counter-based one-time passwords from a base32 secret, listed in a table.

Hreflang Generator

Generate hreflang link tags, headers or sitemap XML for multilingual pages.

HTML Entity Encoder

Escape and unescape HTML entities in any text.

HTML Formatter

Indent messy HTML or collapse it safely, keeping pre and script intact.

HTML Generator

Generate a complete HTML5 boilerplate page from a short form.

HTML Validator

Find unclosed tags, duplicate ids and bad nesting in pasted HTML.

HTTP Header Inspector

Parse pasted HTTP headers, explain each one and audit security.

HTTP Status Codes

Look up what any HTTP status code actually means.

HTTP Status Codes

Every IANA-registered HTTP status code with its RFC.

IANA Media Types

The full IANA MIME type registry with common file extensions.

Image Placeholder Generator

Make sized placeholder images as SVG, PNG, data URI or CSS.

Image Size Calculator

Estimate image file size and see how oversized it is for its slot.

Incident Response Checklist

A step-by-step checklist for the security incident you are facing.

Indent Code

Shift every line right by a set number of spaces or tabs.

Internal Link Analyzer

List a page's links with anchor text, internal/external split, nofollow and repeats.

IP Address Info

Classify any IPv4 or IPv6 address and see its every form.

IP Allowlist Builder

Turn a list of IPs into allow or block rules for your server.

IP Range To CIDR Converter

Turn start and end IP addresses into the fewest CIDR blocks.

IP Subnet Calculator

Network, broadcast, host range and counts for any subnet.

JavaScript Deobfuscation Helper

Decode hidden strings in obfuscated JavaScript and flag risky calls safely.

JavaScript Formatter

Expand minified JavaScript into indented code, or squash it back.

JavaScript Size Calculator

See what a script bundle costs to download and to parse on a phone.

JSON Diff

Compare two JSON documents and list every change by path.

JSON Formatter

Format, minify and validate JSON, with located errors.

JSON Generator

Generate realistic mock JSON records from a simple name and type list.

JSON To YAML Converter

Convert JSON to YAML and YAML back to JSON.

JSON Tree Viewer

Browse JSON as a collapsible tree with the path to every value.

JSONPath Tester

Run JSONPath queries against pasted JSON and see every match.

JWKS Inspector

List every key in a JWKS and flag leaks, weak keys and duplicates.

JWT Decoder

Decode a JWT and read its claims and expiry.

JWT Encoder

Sign a JSON payload into an HS256, HS384 or HS512 JWT.

JWT Signature Verifier

Verify a JWT's signature with a secret, PEM key or JWKS.

Keycode Tester

Press a key and see exactly what your browser reports.

Lighthouse Score Explainer

See exactly where your Lighthouse performance score comes from.

Line Ending Converter

Convert text between LF, CRLF and CR line endings instantly.

LLM API Prices

Per-million-token API prices for 82 models from six vendors.

LLM Cost Calculator

Price LLM API calls per request and per month, with caching.

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MAC Vendor Prefixes

Find the manufacturer behind a MAC address from the IEEE OUI registry.

Markdown Cheat Sheet

CommonMark and GitHub Markdown syntax on one printable page.

Markdown Formatter

Tidy headings, lists, tables and spacing in Markdown.

Memorable Password Generator

Random words, a symbol and digits — strong, and you can remember it.

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Mermaid Live Editor

Type Mermaid syntax, preview it live and download SVG or PNG.

Meta Tag Generator

Generate the head meta tags a page needs, with robots and canonical done right.

MIME Type Lookup

Look up the MIME type for an extension, or the reverse.

Modulo Calculator

Find a mod n for huge or negative numbers in every convention.

Multi Decoder

Detect and unwrap nested Base64, URL, hex and entity encodings automatically.

NTLM Hash Generator

Windows NTLM and LM hashes of a password, computed in your browser.

OAuth PKCE Generator

PKCE code verifier and S256 challenge for OAuth 2.0 testing.

OAuth State And Nonce Generator

Random OAuth state and OpenID nonce values for sign-in testing.

OBS Scene Size Calculator

Size and centre an OBS source, and find your output resolution.

Otpauth URI Decoder

Break an otpauth:// 2FA link into issuer, secret and settings.

OWASP Top 10 Reference

The OWASP Top 10 web risks with plain explanations and fixes.

Page Weight Calculator

Add up page resources, see the breakdown and load time on each connection.

Passphrase Generator

Diceware passphrases from the EFF wordlist, generated locally.

Password Generator

Strong random passwords generated in your own browser.

Password Hash Generator

Argon2id, scrypt and PBKDF2 password hashes with OWASP defaults.

Password Hash Identifier

Identify bcrypt, Argon2, sha512crypt, NTLM, MD5 and other hash formats.

Password Policy Generator

Write a modern NIST-based password policy for your organisation.

Password Policy Tester

Test a list of passwords against length, character and banned-word rules.

Password Strength Checker

Estimate a password's entropy, crack time and weak patterns.

PEM Inspector

Decode PEM and DER into a readable ASN.1 tree.

PEM To JWK Converter

Convert public and private keys between PEM and JWK.

Performance Budget Calculator

Turn a load-time target into a byte budget for each part of the page.

Podcast RSS Item Builder

Build a valid podcast RSS item with enclosure and iTunes tags.

Port Number Lookup

See what runs on a port and whether exposing it is risky.

Prime Number Checker

Check if a number is prime, or list the primes in a range.

Prompt Diff

Compare two prompt versions and see exactly what changed.

Prompt Formatter

Turn loose notes into a structured prompt with XML tags or headings.

RAG Chunk Calculator

Plan chunk size and overlap for retrieval-augmented generation.

Random Date Generator

Random dates between two dates, with weekday filters and formats.

Random PIN Generator

Random 4, 6 or 8 digit PINs, avoiding 1234 and 0000.

Random String Generator

Cryptographically random strings in any length and character set.

Regex Cheat Sheet

Regular expression syntax with examples, printable and downloadable.

Regex Generator

Build a regex from a preset or from sample strings, ready to paste.

Regex Search And Replace

Bulk find and replace with regular expressions.

Regex Tester

Test a regex and see every match and capture group.

Resource Hint Generator

Generate correct preconnect, preload and prefetch tags with the right attributes.

Responsive Image Generator

Generate srcset, sizes and picture markup for responsive images.

Robots.txt Checker

Check a robots.txt file line by line before you deploy it.

Robots.txt Sensitive Path Checker

Spot robots.txt rules that point attackers at sensitive paths.

RSA Key Generator

RSA key pairs as PEM or JWK, made in your browser.

Secret Scanner

Find leaked API keys, tokens and passwords in pasted code.

Secret Splitter

Split a secret into shares; any threshold of them rebuilds it.

Security Headers Checker

Check pasted response headers for missing, weak and leaky security headers.

Security Headers Generator

Generate HTTP security headers for nginx, Apache, Netlify and Express.

SemVer Tool

Sort, compare and bump semantic version numbers.

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Sequence Diagram Maker

Type A -> B message lines and get a sequence diagram.

SERP Preview

Preview your page title and description as a Google search result.

Server Name Generator (Discord, Minecraft)

Discord and Minecraft server names like The Lantern Room and Emberfall SMP.

Signature Verifier

Check whether a signature over a message matches a public key.

Skip Link Generator

Generate a skip-to-content link that appears on focus, with HTML and CSS.

SPF Record Generator

Build an SPF record from the email services you actually use.

SQL Formatter

Turn a one-line SQL query into readable indented SQL.

SRI Hash Generator

Subresource Integrity hashes and tags for scripts and stylesheets.

SRT / VTT Converter

Convert SRT subtitles to WebVTT and back, with an optional time shift.

SSH Key Converter

Convert SSH public keys between OpenSSH, SSH2 and PEM formats.

SSH Key Fingerprint

Get ssh-keygen style SHA256 and MD5 fingerprints from any public key.

SSL Certificate Inspector

Decode a PEM certificate and check its dates, names and fingerprints.

String Escaper

Turn raw text into a safe string literal in any language.

String Unescaper

Decode backslash escapes and quoted literals back into plain text.

SVG Validator

Find unclosed tags, bad path data and broken references in SVG.

Tailwind Colour Converter

Convert hex codes to the nearest Tailwind class, or Tailwind classes to hex.

Tailwind To CSS

Turn Tailwind utility classes into plain CSS declarations.

TB To PB

Convert terabytes to petabytes: divide by 1,000, or 1,024 for binary.

Text To Hex Converter

Convert text to hexadecimal bytes and back again.

TLS Cipher Suites

Every IANA TLS cipher suite with its code, parts and status.

TOTP Generator

Live two-factor codes from a base32 secret, with a countdown.

TOTP QR Code Generator

Authenticator app setup QR codes from a secret, issuer and account.

Unicode Converter

Convert text to and from code points, escapes, entities and UTF-8 bytes.

Unindent Code

Remove common or fixed indentation from a block of code.

URL Encoder / Decoder

Percent-encode and decode URLs, values and form data.

URL Query Parser

Split a URL into a readable table of parameters.

URL Validator

Check a list of URLs for syntax errors, one per line.

User Agent Parser

See what browser and OS a User-Agent string claims to be.

UTM Campaign URL Builder

Build correctly encoded UTM campaign links with consistent naming.

UUID Decoder

Decode a UUID into version, variant, timestamp, clock sequence and node.

UUID Generator

Random v4 or time-ordered v7 UUIDs, generated in your browser.

UUID Validator

Check a list of UUIDs and decode their version, variant and timestamp.

Video Embed Code Generator

Get responsive embed code for YouTube, Vimeo or a video file.

Video For Web Snippet

Write the HTML5 video tag for a self-hosted clip, done properly.

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Video To Sprite Sheet

Make thumbnail sprites and a WebVTT file for video scrub previews.

Web App Manifest Generator

Generate a PWA manifest.webmanifest with icons, colours and head tags.

Webhook Payload Viewer

Flatten any JSON webhook payload into searchable paths and values.

Week Number Calculator

The ISO week number for today or any date.

What Is My IP

See the public IP address every website sees when you connect.

WiFi Password Generator

WPA2/WPA3 keys with no look-alike characters, easy to read aloud.

XML Formatter

Indent messy XML or squash it to one line, with tag checking.

XML Sitemap Generator

Turn a list of URLs into a valid sitemap.xml in seconds.

XML To JSON Converter

Convert XML to JSON and JSON back to XML.

XOR Cipher

XOR with a repeating key, or brute-force every single-byte key.

XPath Tester

Test XPath expressions against pasted XML or HTML instantly.

YAML Formatter

Tidy inconsistent YAML and pinpoint syntax errors by line.