21 Developer Tools You Can Use Without Installing Anything (2026)

I got a new laptop last week. Before installing anything, I needed to format a JSON blob, encode a URL, and check a hash. All three took under 30 seconds — no installs, no terminals, no signups. Just browser tabs.

Here are 21 online developer tools that replace the things you would normally install or script yourself. All free. All work in any browser.

Data Formatting

JSON Formatter — Paste ugly JSON, get indented, collapsible tree view with validation and line numbers. Also minifies back to single-line for production. Made for the "I just got a 3000-character JSON blob from an API" scenario.

JSON to CSV Converter — Flattens nested JSON arrays into spreadsheet-ready CSV. Handles nested objects by flattening keys with dot notation. No Excel macro required.

CSV to JSON Converter — The reverse. Paste a CSV and get a JSON array of objects. Detects headers automatically. Picks the right data types instead of making everything a string.

Encoding and Decoding

Base64 Encoder/Decoder — Standard and URL-safe Base64 in both directions. For when you are reading JWT payloads, embedding images as data URIs, or decoding Basic auth headers.

URL Encoder/Decoder — Encodes spaces, symbols, and Unicode for URL safety. Also decodes percent-encoded URLs back to readable text. Solves the "why is my link broken" problem in one click.

HTML Entities Encoder/Decoder — Converts < to < and back. Useful when embedding code snippets in HTML or cleaning up escaped text from an API.

Hashing and Security

Hash Generator — SHA-1, SHA-256, SHA-384, SHA-512, MD5. Hash any text and compare two hashes side by side. For verifying file checksums.

Password Generator — Cryptographically secure random passwords using Web Crypto API. Choose length and character types. Generated locally — nothing sent to any server.

UUID Generator — Generates v4 UUIDs. One click, one UUID. Click again for another. No libraries, no imports.

Text and Code

Markdown Preview — Write Markdown on the left, see rendered output on the right. GitHub Flavored Markdown. Catches formatting mistakes before you push.

CSS Minifier — Strips whitespace, comments, and unnecessary characters from CSS. Smaller file, faster load.

Regex Tester — Write a regex, test it against sample text, see matches highlighted in real time. No more "works on my machine" surprises.

Case Converter — Convert between UPPERCASE, lowercase, Title Case, camelCase, snake_case, and kebab-case.

Text Diff Checker — Paste two versions of text, see what changed. Line-by-line comparison with additions and deletions highlighted.

Generators and Utilities

Text to Slug — Converts "My Blog Post Title!" to "my-blog-post-title". For URLs, file names, and IDs.

Lorem Ipsum Generator — Generates placeholder text by paragraph, sentence, or word count. For mockups and testing.

Word Counter — Character, word, sentence, and paragraph counts. Plus reading time estimate.

Duplicate Line Remover — Paste a list, remove duplicates, sort alphabetically. For cleaning up email lists and data imports.

The Browser-Only Advantage

All of these tools run entirely in your browser. No data is uploaded to any server. No account required. No ads. No "pro" upsells. Just the tool, doing one thing, right there in a tab.

Bookmark the ones you use most. Keep the rest in the back of your mind for when you need them. That is the whole point of online tools — there when you need them, invisible when you do not.