Small developer tools that respect your time — and your data.

DevKit is a small set of free tools for developers, designers, and marketers in the United States. Format a messy JSON response, check whether a color combination is readable, or encode a string for a URL — right in your browser, with nothing uploaded to a server and nothing to install.

Format some JSON

The tools

JSON Formatter & Validator

Paste in a JSON response from an API and get it back readable, with real indentation — or minified down to one line. If the JSON is broken, the validator points to the exact line and column where the parser stopped, instead of a vague error.

Format JSON →

Color Converter & Contrast Checker

Convert a color between HEX, RGB, and HSL in one click, and check the WCAG contrast ratio between any two colors. Know before you ship whether your text passes AA or AAA — and fix it before a user has to squint.

Convert a color →

Base64 & URL Encoder

Encode text to Base64 (with proper UTF-8 handling for emoji and non-English text) or decode it back, and percent-encode a string for a safe URL query. The kind of small encoding job that comes up ten times a week.

Encode a string →

How to use this site

Pick the job you have. Debugging an API response? Use the JSON formatter. Choosing colors for a page or an email? Use the color converter. Building a link or an API token? Use the Base64 and URL encoder.
Paste, click, copy. Every tool works in one pass: paste your input, click the button, and copy the result. Nothing is uploaded, stored, or sent anywhere.
Read the worked example. Every tool page walks through one full example with verified numbers, so you can check the tool against a known answer before trusting it with your own data.
Read the guide behind the tool. The articles explain the ideas the tool assumes you know: how JSON errors happen, how contrast ratios are calculated, and when Base64 is the right choice — and when URL encoding is.

Guides

How to Format JSON and Fix the Errors That Break It — the five mistakes that break JSON most often, and how to find each one fast.
Accessible Color Contrast: A Practical WCAG Guide — what the 4.5:1 and 7:1 ratios mean, how luminance works, and how to fix a failing palette.
Base64 vs. URL Encoding: What Each One Is For — two encodings that look similar and solve different problems, with examples of when to use each.

Why these three tools?

Developers and marketers hit the same three small jobs again and again: read a blob of data, pick colors people can actually read, and put text safely into a URL or a token. Each job takes thirty seconds with the right tool and ten frustrating minutes without one — hunting through a one-line API response, guessing whether light gray text on a white background is readable, or hand-encoding an ampersand and hoping the link still works. These tools exist to make the thirty-second version the default.

They are deliberately small. A tool that does one job well, loads instantly, and never asks for your data is more useful than a dashboard of fifty half-finished utilities. Every tool on this site runs entirely in your browser: the text you paste never leaves your device. That is not a privacy slogan; it is how the code is written — there is no server endpoint to send it to.

Your input stays on your device

All three tools run entirely in your browser. The JSON, colors, and text you enter are not sent to a server, stored, or shared. Read the full Privacy Policy for details, including how advertising cookies work if ads are shown on this site in the future.

DevKit is run by an independent writer and builder. Learn more on the About page, meet the author on the author page, or get in touch.