# API URL Kit

> A growing hub of focused mini apps for developers and everyday tasks — converters, calculators, formatters, generators and more. Most tools run entirely client-side in the browser — nothing you paste is uploaded to a server. No signup, no installation.

## Categories
- [Image](https://apiurlkit.com/g/image/): Convert, resize, compress and inspect images — without uploading them anywhere.
  - [Convert](https://apiurlkit.com/c/image-convert/): Change image formats — JPG, PNG, WebP, AVIF, HEIC and SVG — in your browser.
  - [Edit & Optimise](https://apiurlkit.com/c/image-edit/): Resize, crop, compress and clean up images before you ship them.
  - [Colour & Design](https://apiurlkit.com/c/color/): Convert colour formats, build palettes and check contrast.
- [AI Tools](https://apiurlkit.com/g/ai/): Summarise, rewrite, generate and clean up content with AI assistance.
  - [AI Writing](https://apiurlkit.com/c/ai-text/): Summarise, rewrite, translate and expand text with AI.
  - [AI Image](https://apiurlkit.com/c/ai-image/): Remove backgrounds, upscale and clean up images automatically.
- [Files & Data](https://apiurlkit.com/g/files/): Convert between document and data formats — CSV, JSON, YAML, Markdown and more.
  - [Document Convert](https://apiurlkit.com/c/file-convert/): Move between document formats such as Markdown, HTML and text.
  - [Data Convert](https://apiurlkit.com/c/data-convert/): Convert between CSV, JSON, YAML, XML and other structured formats.
- [Developer](https://apiurlkit.com/g/developer/): Utilities for working with APIs, data formats, encoding and the web platform.
  - [Data & URLs](https://apiurlkit.com/c/data-urls/): Extract, clean, parse and build URLs and structured data from API responses.
  - [Encoding & Crypto](https://apiurlkit.com/c/encoding/): Encode, decode, hash and inspect tokens — Base64, JWT, hashes and IDs.
  - [Formatting & Validation](https://apiurlkit.com/c/formatting/): Pretty-print, minify, convert and validate JSON, YAML, XML, SQL and more.
  - [Regex & Patterns](https://apiurlkit.com/c/regex/): Write, test and understand regular expressions and pattern-matching rules.
  - [Web & DevOps](https://apiurlkit.com/c/web-devops/): Headers, cron expressions, environment files and everyday operations helpers.
- [Text](https://apiurlkit.com/g/text/): Compare, transform, clean and analyse text of any size.
  - [Compare & Diff](https://apiurlkit.com/c/text-compare/): Spot exactly what changed between two versions of text or data.
  - [Transform & Case](https://apiurlkit.com/c/text-transform/): Change case, sort, deduplicate, slugify and reshape blocks of text.
  - [Count & Analyse](https://apiurlkit.com/c/text-analysis/): Word, character and readability statistics for writing and content work.
- [Video & Audio](https://apiurlkit.com/g/video-audio/): Convert, trim and extract from video and audio files.
  - [Video](https://apiurlkit.com/c/video-tools/): Convert, trim, mute and turn video into GIFs.
  - [Audio](https://apiurlkit.com/c/audio-tools/): Convert audio formats, trim clips and extract sound from video.
- [Calculators](https://apiurlkit.com/g/calculators/): Everyday maths, unit conversion, dates and health metrics you keep redoing.
  - [Everyday Maths](https://apiurlkit.com/c/calculators/): Percentages, ratios, averages and the arithmetic you keep redoing.
  - [Units & Measures](https://apiurlkit.com/c/units/): Length, weight, temperature, area, speed and data-size conversion.
  - [Time & Dates](https://apiurlkit.com/c/time/): Timestamps, time zones, durations and date arithmetic in both directions.
- [Money](https://apiurlkit.com/g/finance/): Loans, interest, tax, currency and salary calculators.
  - [Money & Finance](https://apiurlkit.com/c/finance/): Loans, interest, tax, currency and salary calculators.
- [Productivity](https://apiurlkit.com/g/productivity/): Lists, planning and generators that keep work moving.
  - [Lists & Planning](https://apiurlkit.com/c/planning/): Checklists, trackers and lightweight planning tools.
  - [Generators](https://apiurlkit.com/c/generators/): Produce IDs, passwords, mock data, placeholders and sample content.

## Tools
- [API URL Extractor](https://apiurlkit.com/tools/url-extractor/): Unescape, extract, validate, filter and preview URLs from JSON, REST, GraphQL, Postman and Insomnia API responses.
- [Checklist Tracker](https://apiurlkit.com/tools/checklist/): Turn Markdown or JSON into interactive project checklists with progress tracking, multiple lists, and one-click export.
- [EXIF Remover](https://apiurlkit.com/tools/exif-remover/): See the hidden metadata in a photo — including where it was taken — and download a clean copy without it.
- [cURL to Code](https://apiurlkit.com/tools/curl-to-code/): Convert a cURL command into fetch, Axios, Python requests, httpx or Go — in your browser.
- [Age Calculator](https://apiurlkit.com/tools/age-calculator/): Work out an exact age, or the span between any two dates, in years, months, days, weeks and working days.
- [JWT Decoder](https://apiurlkit.com/tools/jwt-decoder/): Decode JSON Web Token headers and payloads to inspect claims without sending them anywhere.
- [Bill Splitter](https://apiurlkit.com/tools/bill-splitter/): Split a bill by what each person actually ordered, share the tip fairly, and see the fewest payments that settle everyone up.
- [Diff Checker](https://apiurlkit.com/tools/diff-checker/): Compare two blocks of text or JSON line by line and see exactly what was added, removed or changed.
- [OpenAPI Viewer](https://apiurlkit.com/tools/openapi-viewer/): Preview OpenAPI and Swagger specs as readable docs with sample responses — no Docker, no upload.
- [Webhook Signature Verifier](https://apiurlkit.com/tools/webhook-verifier/): Verify Stripe, GitHub, Shopify and Slack webhook HMAC signatures locally in your browser.
- [Regex Tester](https://apiurlkit.com/tools/regex-tester/): Test regular expressions against sample text with live match highlighting, capture groups and flags.
- [Timestamp Converter](https://apiurlkit.com/tools/timestamp-converter/): Convert between Unix timestamps (seconds or milliseconds), ISO 8601, UTC and your local time — both directions.

## Coming soon
- [JPG to PNG Converter](https://apiurlkit.com/tools/jpg-to-png/): Convert JPG and JPEG images to lossless PNG right in your browser — no upload, no watermark, no queue.
- [Password Generator](https://apiurlkit.com/tools/password-generator/): Generate strong random passwords with control over length, symbols and ambiguous characters.
- [Image Compressor](https://apiurlkit.com/tools/image-compressor/): Shrink JPG, PNG and WebP file sizes with a live preview of quality against bytes saved.
- [PNG to JPG Converter](https://apiurlkit.com/tools/png-to-jpg/): Turn PNG images into compressed JPG files with a quality slider and a background colour for transparency.
- [Image Resizer](https://apiurlkit.com/tools/image-resizer/): Resize images to exact pixel dimensions or a percentage, with the aspect ratio locked by default.
- [WebP Converter](https://apiurlkit.com/tools/webp-converter/): Convert images to and from WebP to cut page weight without visible quality loss.
- [CSV to JSON Converter](https://apiurlkit.com/tools/csv-to-json/): Turn CSV or TSV into clean JSON, with header detection and type inference.
- [AI Text Summariser](https://apiurlkit.com/tools/ai-summarizer/): Condense long articles, documents or transcripts into a short summary or bullet points.
- [Unit Converter](https://apiurlkit.com/tools/unit-converter/): Convert length, weight, temperature, area, volume, speed and data size in one place.
- [AI Background Remover](https://apiurlkit.com/tools/ai-background-remover/): Cut the background out of a photo automatically and download a transparent PNG.
- [Word Counter](https://apiurlkit.com/tools/word-counter/): Count words, characters, sentences and paragraphs, with reading time and keyword density.
- [JSON Formatter](https://apiurlkit.com/tools/json-formatter/): Pretty-print, minify and validate JSON with clear error messages — all client-side.
- [JSON to YAML Converter](https://apiurlkit.com/tools/json-to-yaml/): Convert JSON to YAML and back, preserving key order and nesting.
- [UUID Generator](https://apiurlkit.com/tools/uuid-generator/): Generate v4 UUIDs singly or in bulk, ready to copy or download.
- [Colour Converter](https://apiurlkit.com/tools/color-converter/): Convert colours between HEX, RGB, HSL, HSV and CSS names, with a live swatch.
- [Loan Calculator](https://apiurlkit.com/tools/loan-calculator/): Work out monthly repayments, total interest and an amortisation schedule for any loan.
- [Percentage Calculator](https://apiurlkit.com/tools/percentage-calculator/): Work out percentages, percentage change and reverse percentages without second-guessing the formula.
- [AI Rewriter](https://apiurlkit.com/tools/ai-rewriter/): Rewrite text to change tone, shorten it, or make it clearer while keeping the meaning.
- [Base64 Encode / Decode](https://apiurlkit.com/tools/base64/): Encode text to Base64 or decode Base64 back to text and data URIs, privately in your browser.
- [Markdown to HTML](https://apiurlkit.com/tools/markdown-to-html/): Convert Markdown into clean, semantic HTML you can paste anywhere.
- [Case Converter](https://apiurlkit.com/tools/case-converter/): Switch text between camelCase, snake_case, kebab-case, Title Case, UPPER and lower.
- [Video to GIF](https://apiurlkit.com/tools/video-to-gif/): Turn a short video clip into an optimised animated GIF with control over frame rate and size.
- [Cron Expression Generator](https://apiurlkit.com/tools/cron-expression-generator/): Build and read cron expressions in plain English, with the next run times shown.
- [Audio Converter](https://apiurlkit.com/tools/audio-converter/): Convert audio between MP3, WAV, OGG and M4A without installing anything.

## Collections
- [All tools](https://apiurlkit.com/tools/): the full catalogue of 36 mini apps.
- [Free, private, browser-based tools](https://apiurlkit.com/private-tools/): the subset that processes everything on your own device.

## Guides
- [From Copy as cURL to Production Code, Without the Copied Secrets](https://apiurlkit.com/blog/curl-to-production-code.html): Turning a Copy as cURL command from DevTools into clean client code — how each flag maps onto fetch, Axios, requests, httpx and net/http, and how to avoid committing the credentials that came along for the ride.
- [Debugging JWTs Client-Side: Header, Claims, Expiry and Privacy](https://apiurlkit.com/blog/debugging-jwts-client-side.html): What is actually inside a JSON Web Token, why pasting a live one into an online decoder hands over a working credential, and how to read the claims that explain most authentication failures.
- [Extracting and Cleaning URLs from Large API Responses, Safely](https://apiurlkit.com/blog/safely-extract-urls-from-json.html): Pulling every link out of a large REST, GraphQL or Postman response without pasting proprietary data into a server-side parser — including the escaping, filtering and edge cases that make the job fiddly.
- [Base64 Encoding Explained (and the Mistake Everyone Makes)](https://apiurlkit.com/blog/base64-encoding-explained.html): What Base64 actually does, why it makes data roughly a third larger, the difference between standard and URL-safe alphabets, and the one mistake that causes most Base64 bugs in production.
- [Browser-Based Developer Tools: Why Client-Side Beats Uploading](https://apiurlkit.com/blog/browser-based-developer-tools.html): Why client-side developer tools are usually the right default, what actually happens to data you paste into an online utility, and how to tell the two kinds apart before you paste anything sensitive.
- [Unix Timestamps: Seconds, Milliseconds and the 2038 Problem](https://apiurlkit.com/blog/unix-timestamps-explained.html): How Unix time works, how to tell seconds from milliseconds at a glance, why leap seconds make it not-quite-elapsed-time, and what the year 2038 problem actually breaks.
- [How to Extract All URLs from an API Response](https://apiurlkit.com/blog/extract-urls-from-api-responses.html): A no-code workflow to extract every image, video and link URL from REST, GraphQL, Postman and Insomnia responses, then filter, dedupe and export the list without writing a throwaway script.
- [Why JSON URLs Contain Backslashes (and How to Fix Them)](https://apiurlkit.com/blog/why-json-urls-have-backslashes.html): Learn why URLs in JSON and API responses show up as https:\/\/example.com, why the escaping is valid rather than a bug, and how to unescape them instantly without writing a regex.

## About
- [About](https://apiurlkit.com/about.html): what API URL Kit is and why it exists.
- [Privacy](https://apiurlkit.com/privacy.html): how tools handle your data.
- [Blog](https://apiurlkit.com/blog/): guides on working with URLs and API data.
- [Contact](https://apiurlkit.com/contact.html)