# jigg.dev > Small, free, fun tools by Caleb Terry. Every tool runs in the visitor's browser: nothing typed or uploaded is sent to a server or stored. Most tools keep their state in the URL, so a link reopens the same result. In browsers with WebMCP (`navigator.modelContext`), every page registers the agent tools listed below, so an assistant can call them directly instead of driving the page. ## Tools - [QR scanner](https://jigg.dev/tools/qr-scanner): Scan a QR code with your camera or from a screenshot, and see what's inside before you open it. - [Color blindness simulator](https://jigg.dev/tools/color-blindness): See an image or a set of colors the way people with red, green or blue color blindness do. - [Aspect ratio calculator](https://jigg.dev/tools/aspect-ratio): Simplify any size to its ratio, and resize to a ratio without doing the math. - [Date difference](https://jigg.dev/tools/date-diff): Count the years, months, days and weekdays between two dates, or add days to a date. - [CSV to JSON](https://jigg.dev/tools/csv-json): Convert CSV to JSON and back, with quoted fields, delimiter detection and typed values. - [Number base converter](https://jigg.dev/tools/base-converter): Convert whole numbers between binary, octal, decimal, hex and any base up to 36. - [Color palette](https://jigg.dev/tools/color-palette): Turn one color into a full 50-950 scale and matching harmonies, then export it as CSS or Tailwind. - [Markdown preview](https://jigg.dev/tools/markdown-preview): Write Markdown with GitHub's extras and see it rendered live, then copy the HTML. - [Unit converter](https://jigg.dev/tools/unit-converter): Convert length, weight, temperature, volume, area, speed, data and time, all at once. - [Hash generator](https://jigg.dev/tools/hash-generator): Get MD5, SHA-1, SHA-256, SHA-384 and SHA-512 of text or a file, and check it against a hash. - [Crontab editor](https://jigg.dev/tools/cron-editor): Build a cron schedule by clicking, read it in plain English, and see exactly when it runs next. - [JWT decoder](https://jigg.dev/tools/jwt-decoder): Read a JSON Web Token's header and claims, see when it expires, and check an HMAC signature. - [UUID generator](https://jigg.dev/tools/uuid-generator): Make UUID v4, v7 or ULID IDs in bulk, and inspect any ID to see its version and timestamp. - [Text diff](https://jigg.dev/tools/text-diff): Compare two texts line by line, with the changed words highlighted. - [Image compressor](https://jigg.dev/tools/image-compressor): Shrink and resize images to WebP, AVIF or JPEG right in your browser; nothing is uploaded. - [Regex tester](https://jigg.dev/tools/regex-tester): Test a regular expression live, see every match and group, and read it in plain English. - [Encode & decode](https://jigg.dev/tools/encoder): Convert text to and from Base64, URL encoding and HTML entities. - [Contrast checker](https://jigg.dev/tools/contrast-checker): Check two colors against WCAG AA and AAA, and get the nearest color that passes. - [Word counter](https://jigg.dev/tools/word-counter): Count words and characters, see reading time, and check social post limits. - [Time zones](https://jigg.dev/tools/time-zones): Find a meeting time that works across cities, hour by hour. - [JSON formatter](https://jigg.dev/tools/json-formatter): Pretty-print, minify and sort JSON, with errors pointed out by line. - [QR code maker](https://jigg.dev/tools/qr-code): Turn a link, text or Wi-Fi login into a QR code you can download. - [Password generator](https://jigg.dev/tools/password-generator): Make a strong random password; it never leaves your browser. - [Timestamps](https://jigg.dev/tools/timestamp-converter): Convert Unix timestamps to dates and back, in UTC and your time zone. - [Random color](https://jigg.dev/tools/random-color): Roll a random color and copy it as hex, RGB or HSL. ## Agent tools (WebMCP) - `list_tools`: Every tool on jigg.dev with its URL, one-line description and tags. - `open_tool`: Navigates this tab to one of the site's tools, so the person can use it themselves. - `convert_number_base`: Converts a whole number (any size) from one base (2-36) to binary, octal, decimal, hex and an optional extra base. - `convert_units`: Converts a value between units of length, weight, temperature, volume, area, speed, data, time. - `csv_to_json`: Parses CSV (quoted fields and newlines in cells are fine) into JSON rows. - `json_to_csv`: Turns a JSON array of objects (keys become columns) or of arrays into CSV. - `date_difference`: Years, months and days between two dates, plus total days, weeks and business days (Mon-Fri). - `aspect_ratio`: Simplifies a width and height to a ratio (1920x1080 is 16:9), names the nearest common ratio, and optionally solves a new size at that ratio. - `check_contrast`: WCAG 2.2 contrast ratio of a text color on a background, and which levels (AA, AAA, large text, UI) it passes. - `color_palette`: A 50-950 shade scale of one color, plus a matching harmony (complementary, analogous, triadic, split, tetradic). - `generate_password`: A random password from the browser's crypto randomness, with at least one character from each chosen set. Never leaves the device. - `generate_ids`: Random UUID v4, time-ordered UUID v7, or ULID values. - `hash_text`: Hex digest of UTF-8 text with MD5, SHA-1, SHA-256, SHA-384, SHA-512. - `encode_text`: Base64, Base64URL, URL (percent) or HTML entity encoding. - `decode_jwt`: Reads a JSON Web Token's header and payload. Does not check the signature. - `format_json`: Pretty-prints or minifies JSON, optionally sorting keys; invalid JSON comes back with the line and column of the error. - `count_words`: Words, characters, sentences, paragraphs and reading and speaking time of a text. - `test_regex`: Runs a JavaScript regex over text and returns the matches with their groups, plus a plain-English reading of the pattern. - `explain_cron`: Describes a five-field cron expression (or @daily style macro) in plain English and lists its next run times in UTC. - `convert_timestamp`: Reads Unix seconds, Unix milliseconds or a date string and returns it in common formats. ## Optional - [For AI agents](https://jigg.dev/agents): this page for people, with every agent tool's inputs - [Changelog](https://jigg.dev/changelog): every tool, newest first - [RSS feed](https://jigg.dev/feed.xml): new tools - [Sitemap](https://jigg.dev/sitemap.xml)