Developer Tools
Encode, decode, hash, format and generate the small things a build needs. Every tool runs entirely in your browser using the Web Crypto and standard JS APIs already built into it - nothing you paste is ever sent to a server.
Base64 Encoder/Decoder A Base64 encoder and decoder that handles emoji and accented characters correctly, with a URL-safe mode. URL Encoder/Decoder A URL encoder/decoder with an explicit choice between escaping a single value and encoding a whole address. HTML Entity Encoder/Decoder Turn special characters into safe HTML entities, or decode entities back into readable text. JWT Decoder Read a JWT's header and payload without needing the signing secret, and see at a glance whether it has expired - and explicitly explains, rather than glossing over, why decoding is not verifying, a distinction many tools leave unsaid. UUID Generator A UUID generator built for bulk use - up to 1,000 at once, in either version-4 (fully random) or version-7 (time-ordered, increasingly the default choice for database primary keys) - plus a decoder that reads the version, variant, and embedded timestamp back out of any UUID you paste in. Hash Generator Every common hash of your text, side by side, with an honest note about which ones are safe to rely on. Number Base Converter A number base converter that stays exact even far beyond what a standard calculator can represent precisely. Regex Tester A regex tester that highlights every match in context and lists capture groups, positions and named groups. Unix Timestamp Converter A two-way Unix timestamp converter with ISO, UTC, local time and a plain-English relative label all at once. MIME Type / File Extension Lookup A two-way lookup between file extensions and their standard MIME types. User Agent Parser Break down any user agent string into browser, operating system, device type and rendering engine. IP Subnet Calculator An IPv4 subnet calculator that gets the /31 and /32 edge cases right, not just the common /24. HTML Formatter/Minifier An HTML formatter and minifier that leaves the content of pre, textarea, script and style tags untouched. CSS Formatter/Minifier A CSS formatter and minifier that indents nested rules (including media queries) and normalises property:value spacing. JavaScript Formatter/Minifier A JavaScript formatter and minifier that never touches the inside of a string, even one that contains // or /* characters. SQL Formatter/Minifier A SQL formatter that breaks a query onto readable lines by clause, without ever splitting a comma inside a function call. Color Converter A color format converter that reads hex, rgb() or hsl() and shows all three at once. Color Picker A visual color picker with hex/RGB/HSL output and a recently-used color history saved on your device. Color Contrast Checker A contrast checker against all four WCAG thresholds at once, with a live text preview at your actual colors. Color Palette Generator A palette generator using the standard, fixed colour-wheel harmony rules - not a randomised suggestion. Gradient Generator A visual linear/radial gradient builder with up to 5 color stops and instant, ready-to-paste CSS. CSS Snippet Generator Four common CSS snippets - box shadow, border radius, text shadow, rgba color - each with live sliders and a preview. JSON Formatter, Minifier & Validator Paste any JSON and instantly see it beautified, minified, or as a collapsible-free readable tree, with syntax errors reported by message and cause rather than just a red X. JSON to CSV Converter Handles the common case cleanly: a JSON array of flat objects becomes a CSV with a header row built from every key seen across all objects, and CSV converts back to an array of objects using the header row as field names. JSON to XML Converter Uses one clear, disclosed convention in both directions: a JSON key becomes an XML element, arrays repeat that element, and an object key starting with @ becomes an XML attribute instead - since JSON and XML don't map onto each other in only one correct way. JSON to YAML Converter A real YAML parser and dumper under the hood, not a regex substitution, so nested objects, arrays, strings needing quotes, and multi-document quirks are all handled the way an actual YAML processor would handle them. CSV Formatter & CSV to TSV Converter Parses your data with a real RFC-4180-aware parser - so quoted fields containing commas, quotes or line breaks are handled correctly - then re-serialises it cleanly with consistent line endings and only the quoting that's actually needed. CSV to XML Converter Uses the header row as column names by default, wraps every data row in a configurable row element, and sanitises column names that aren't valid XML element names rather than producing broken XML. CSV Column Extractor Reads the actual header row from your CSV and shows a checkbox for every column found, so you pick by name rather than guessing column numbers - and the remaining columns keep their original left-to-right order. CSV Duplicate Remover Compares the full row across every column - not just one key field - and keeps the first occurrence of each unique row, with optional case-insensitive and whitespace-trimmed matching for messy exports. CSV Sorter Lets you sort by any column found in your data, and choose whether to sort it as text or as numbers - so a numeric column sorts 2, 9, 10 in that order instead of the text-sort order of 10, 2, 9. XML Formatter & Minifier Uses the browser's own XML parser to understand real element nesting, attributes, comments and CDATA sections, rather than a regex or brace-matching approach that would get self-closing tags and attribute quoting wrong. XML to CSV Converter Scoped to the common repeated-row shape - one root element containing repeated row elements, each with simple child elements as columns - which is exactly what this site's own CSV-to-XML tool produces, and what most row-oriented XML exports look like. YAML Formatter Parses your YAML with a real YAML library and re-dumps it, which both validates the document and normalises its indentation and quoting in the same step - rather than trying to re-indent YAML text without understanding its structure. Cron Expression Generator Build and explain five-field cron expressions, with plain-English meaning and the next 10 run times. HTML to Markdown Converter Convert HTML to Markdown, with headings, links, lists, tables and code blocks preserved. Markdown to HTML Converter Convert Markdown to HTML with a live preview, tables, lists and code blocks. .htaccess Generator Generate an .htaccess file with HTTPS and www redirects, 301 redirects, gzip, caching and more. Text Encryption Tool Encrypt and decrypt text with AES-256-GCM and a password, entirely in your browser. CSV Splitter Split a large CSV into smaller files by row count or number of parts, with headers kept, in one ZIP. Merge CSV Files Combine several CSV files into one, with columns matched by header name and an optional source column. HTTP Status Code Lookup A searchable HTTP status code reference with meanings, fixes and CSV export. URL Parser Break a URL into parts and decoded query parameters, then copy as JSON or download CSV. ASCII Table Searchable ASCII table with decimal, hex, octal and binary values and control code names. JSON to TypeScript Converter Generate TypeScript interfaces from a JSON sample with optional keys and unions. PX to REM Converter Convert px to rem and back for any base font size, with a reference table. CSS Flexbox Generator CSS Flexbox generator with a live preview and copyable code. CSS Grid Generator CSS Grid generator with a live preview and copyable code. JavaScript Key Code Finder See event.key, event.code, keyCode and modifiers for any key you press. CSV Statistics Tool Count, sum, average, median, min and max per numeric column, straight from pasted CSV. SQL Query Generator Statement type, table, columns, joins and conditions in; clean SQL out, updated live. Regex Builder Pattern built from clickable parts, plain-English explanation, live match testing. HTML Table to CSV Every row extracted in order, merged cells honoured, header kept separate. Image URL Extractor Every img src and srcset found, alt text beside it, placeholders set apart. YouTube URL Parser Every URL format, the video ID, embed snippet and start-time links in one readout. Product CSV Cleaner Whitespace, price formats and case normalised; duplicate SKUs and missing prices flagged. Text to CSV Extractor Three input shapes recognised, separator detected, one row per record out. CIDR Range Converter Minimal CIDR lists from IPv4 ranges, and full network detail from a single CIDR. IP Address Converter Five representations of one IPv4 address, plus its class and whether it is private or reserved. IPv6 Address Formatter RFC 5952 formatting, strict validation and 128-bit prefix ranges, all in the browser. Text Legibility Checker WCAG-based verdicts on the five typography settings that decide whether body text is comfortable to read. SVG Shape Generator Circles, ellipses, rounded rectangles, polygons and stars as editable, handable SVG. CSS Animation Generator Fade, slide, zoom, pulse, spin, bounce or shake - written as CSS you can paste in. Responsive Breakpoint Generator Nine device widths as ready-to-paste media queries, with an optional fluid type scale.
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About these tools
No server round-trip for anything - encoding, hashing and formatting all happen locally, which also means it still works on an internal or offline network.
Every tool in this category runs entirely in your browser. Nothing you type, paste or upload is transmitted to a server, and none of them require an account. That is a consequence of how they are built rather than a policy: there is no server involved in the calculation at all.
Each tool page explains the method behind it - the formula, the convention, or the reference table - and states plainly where the result is an estimate rather than an exact answer.