Developer Tools

Searchable ASCII reference with decimal, hex, octal, binary and escapes.

Generate EAN-13, EAN-8 and UPC-A barcodes as scalable SVG, with the check digit worked out.

Encode and decode Base32 in both the RFC 4648 and Crockford alphabets.

Encode text to Base64 and decode it back, with full Unicode and URL-safe support.

Arithmetic and bitwise operations on 8 to 64-bit integers, in any base.

Round corners individually, including the elliptical eight-value form.

Build a layered CSS box-shadow with live preview, including inset and multi-layer depth.

Convert Unix file permissions between the octal number, the symbolic string and a tick-box grid.

Check any two colours against the WCAG contrast thresholds, with passing shades suggested.

See how two colours look under protanopia, deuteranopia, tritanopia and greyscale.

Build or decode a cron expression, in plain English, with the next run times.

Builds a Content-Security-Policy header and warns about the settings that quietly defeat it.

Build a @keyframes block and its shorthand from a preset, with a live preview and a reduced-motion guard.

Build a fluid clamp() that scales a size between two viewport widths.

Build a flex layout against a live preview and copy CSS containing only the properties you changed.

Format CSS with consistent indentation, or minify it for delivery.

Build a linear, radial or conic CSS gradient visually and copy the declaration.

Build a grid visually — tracks, gaps, alignment and cell spans — and copy the CSS it produces.

Work out the specificity of any selector, with a part-by-part breakdown and a winner when you compare several.

Convert CSV to JSON or JSON back to CSV, with proper quoted-field handling.

Build a CSS easing curve, see it drawn, and read the progress at each moment.

Turn a curl command into fetch, axios, Python requests or Node https code.

Turn a docker run command into a compose.yaml service, with the flags that have no Compose equivalent listed rather than dropped.

Parses raw email headers into the delivery path with hop timings, the SPF, DKIM and DMARC results, and the identity mismatches worth noticing.

Convert .env, .ini and .properties files to JSON, and back again.

Generate SHA-256, SHA-384, SHA-512 or SHA-1 digests of text or a file, and verify a checksum.

Compute a keyed HMAC over a message with SHA-1, SHA-256, SHA-384 or SHA-512.

Escape HTML characters to entities and decode them back, in named, decimal or hex form.

Beautify and indent HTML markup, or minify it for production.

Search every HTTP status code — what it means, when to return it, and whether it caches.

Shows the sign, exponent and significand bits of a float or double, and the exact decimal value those bits stand for.

Work out the network, broadcast, mask and usable host range for any IPv4 CIDR block.

Expand, compress and inspect an IPv6 address, with its scope and integer value.

Read and write durations like PT1H30M, and convert them to seconds, minutes or hours.

Compare two JSON documents by structure — key order and formatting ignored, type changes called out.

Pretty-print, minify and inspect JSON with precise error positions.

Infer a JSON Schema from a sample document, with the guesses spelled out.

Turn a JSON sample into TypeScript interfaces, with optional and union types inferred.

Convert JSON to XML or XML back to JSON, with attributes, text nodes and arrays mapped by a stated convention.

Convert JSON to YAML or YAML back to JSON, with the ambiguous values quoted.

Check JSON validity and get a structural summary — depth, key count and type breakdown.

Runs a JSONPath expression against a document and shows every match with the path it came from.

Decode a JSON Web Token's header, payload and claims, and see whether it has expired.

Reformat a MAC address between notations and read the flags in its first byte.

Build a Markdown table in a grid or from pasted CSV, with column alignment and pipes escaped for you.

Build a linked table of contents from the headings in a Markdown document.

Audit a page's title, description and social tags from its HTML, with card previews.

Find the Content-Type for any file extension, and what to send with it.

Generate a typographic size scale from a base size and a ratio, with CSS output.

What service conventionally runs on a TCP or UDP port, whether it encrypts, and whether exposing it to the internet is a bad idea.

Generate a strong random password with your own length and character rules, and see its real entropy.

Shows what a password's character count hides — the patterns that make it guessable.

Convert internationalised domain names between their Unicode and xn-- forms, with a mixed-script warning.

Create a QR code for a link, Wi-Fi network, contact card or any text, and download it as SVG.

Usable capacity, redundancy cost and fault tolerance for RAID 0, 1, 5, 6, 10, 50 and 60, in both decimal TB and binary TiB.

Draw whole or decimal numbers in any range, with or without repeats, from the browser secure RNG.

Turns a list of old and new URLs into server redirect rules, and finds the loops and chains first.

Test regular expressions live with highlighted matches, capture groups and replace.

Build a robots.txt with per-crawler rules, and get it checked for the usual mistakes.

Generate JSON-LD structured data for articles, businesses, products, events and more.

Order two versions, sort a list, or test whether a version satisfies a caret or tilde range.

Beautify or minify a SQL query, with clause breaks, indented subqueries and keyword casing.

Escape or unescape a string for JSON, JavaScript, SQL, a shell, CSV or a regular expression.

Encrypt a message with a passphrase using AES-256-GCM, and decrypt it back again.

Convert Unix timestamps to human dates and back, in local time and UTC.

Converts TOML config to JSON and back, with a parser that reports the line it failed on rather than guessing.

Enumerate every case of a boolean expression, with working columns and an equivalence check.

Percent-encode and decode URLs and query parameters, with a query string breakdown.

Splits a URL into its components with the query string decoded into a table, and flags the encoding and credential problems in it.

Break a user-agent string into browser, engine, OS and device — and what it cannot tell you.

Generate cryptographically random UUIDs in bulk, with formatting options.

Indent or minify XML and check it is well-formed, without disturbing mixed content or CDATA.

Turn a list of URLs into a valid sitemap.xml, with the fields Google ignores switched off by default.