Free Online Developer Tools
Format, validate, convert and debug code with free browser-based utilities for JSON, Base64, URLs, regex and more. No signup, nothing to install, and your data stays on your device.
JSON Formatter
Paste minified or messy JSON and get readable output with consistent indentation — ideal for inspecting API responses and config files.
Open tool →JSON Validator
Check JSON syntax and see where parsing fails, so you can fix a missing comma or quote before it breaks your app.
Open tool →JSON Minifier
Strip whitespace and line breaks from JSON to shrink API payloads and stored config. The data itself stays unchanged.
Open tool →JSON Repair
Recover broken JSON from LLM output or hand-edited files and get valid, parseable JSON back without fixing it line by line.
Open tool →JSON to Java Converter
Generate Java POJO classes from a JSON sample instead of writing every field and type by hand.
Open tool →Base64 Encoder
Encode text to Base64 for data URIs, HTTP headers and API payloads. Base64 makes data safe to transport — it does not encrypt it.
Open tool →Base64 Decoder
Decode Base64 strings back to readable text to inspect tokens, payloads and encoded configuration values.
Open tool →URL Encoder
Encode or decode URLs and query-string values so spaces and special characters travel safely in links and API calls.
Open tool →Multiple URL Opener
Paste a list of links and open them all in new browser tabs at once — handy for checking pages after a release.
Open tool →UUID Generator
Generate random UUID v4 values for database keys, test fixtures and request IDs in one click.
Open tool →Epoch Time Converter
Convert Unix timestamps to human-readable dates, and dates back to epoch time, when reading logs or debugging APIs.
Open tool →Password Generator
Create strong random passwords with your chosen length and character sets, generated with your browser’s cryptographic random source.
Open tool →Regex Tester
Test regular expressions against sample text and see what matches before you put the pattern into code.
Open tool →Text Diff Checker
Compare two versions of code, config or text side by side and see added, removed and changed lines highlighted.
Open tool →Excel Compare
Compare two Excel or CSV files cell by cell and highlight exactly what changed between versions of a spreadsheet.
Open tool →JavaScript Beautifier
Reformat minified or messy JavaScript into consistently indented, readable code that is easier to review and debug.
Open tool →HTML & CSS Beautifier
Beautify HTML markup and CSS stylesheets with clean indentation so templates and styles are easier to read and edit.
Open tool →Word to HTML Generator
Convert a Word document into a clean, styled HTML page with CSS, ready to publish on the web.
Open tool →Website Builder
Build multi-page websites from templates, 24 content blocks and a brand theme, then export clean HTML and CSS. No account needed.
Open tool →Everyday utilities for working with data and code
Most of a developer’s small, repetitive jobs involve reshaping text: pretty-printing an API response to read it, minifying it to ship it, checking a config file that refuses to load, or turning a JSON sample into a Java class. These tools each do one of those jobs and run in your browser, so pasting a payload with customer data or an access token into them does not send it anywhere.
Pick the tool by the problem you have. If a parser is throwing “Unexpected token”, start with the JSON Validator to find the exact position, then JSON Repair if the input came from a model or a hand-edited file. Once it parses, the JSON Formatter makes it readable and the JSON Minifier shrinks it back down for shipping.
If you are comparing two versions of something, Text Diff handles code and config while Excel Compare works cell by cell on spreadsheets. For encoding questions, the Base64 Encoder and Base64 Decoder work as a pair, as does the URL Encoder — but remember that encoding makes data safe to transport; it does not hide it. When front-end code arrives minified, run it through the JavaScript Beautifier and the HTML & CSS Beautifier before you start reading.
Why use Neemtools developer tools?
- Free to use, with no signup and nothing to install — open a tool and paste your input.
- Processing happens in your browser, so code, tokens and payloads are not uploaded to a server.
- One job per page, with related tools linked so you can move from validating to formatting to comparing.
- Works on desktop and mobile browsers.
Related guides: How to fix common JSON errors · Unix timestamps explained
Frequently Asked Questions
What are online developer tools?
Online developer tools are small web utilities for everyday programming tasks — formatting and validating JSON, encoding Base64 and URLs, testing regular expressions, comparing files, and beautifying code — that you use in a browser instead of installing software.
Which developer tools are available on Neemtools?
JSON Formatter, JSON Validator, JSON Minifier, JSON Repair, JSON to Java Converter, Base64 Encoder and Decoder, URL Encoder/Decoder, Multiple URL Opener, UUID Generator, Epoch Time Converter, Password Generator, Regex Tester, Text Diff Checker, Excel Compare, JavaScript Beautifier, HTML & CSS Beautifier, Word to HTML Generator, and Website Builder.
Are these developer tools free?
Yes. Every developer tool on Neemtools is free to use, with no signup, account, or usage limit.
Is my source code or data uploaded to a server?
No. These tools run entirely in your browser, so the text, code, and files you paste are processed on your device and are not sent to Neemtools.
Do I need to install anything?
No. The tools work in any modern browser — there is no extension, desktop app, or command-line package to install.
Can I use these developer tools on mobile?
Yes. The pages are responsive and work in mobile browsers, although large files and long code are easier to work with on a desktop screen.
Which tool should I use to fix invalid JSON?
Start with the JSON Validator to find where parsing fails. If the JSON came from an LLM or a hand-edited file and has several problems, JSON Repair can fix common mistakes automatically. Then use the JSON Formatter to make the result readable.