Free Online Developer Tools
A suite of 979 hyper-fast utilities — JSON formatter, Base64, hashing, converters, generators & more. All of them run locally in your browser, so the JSON, tokens and config you paste in never touch a server.
Start here
The twelve tools people reach for most. Everything else is in the full directory.
JSON Formatter
Format, validate, and beautify JSON payloads.
Base64 Encoder
Encode or decode Base64 strings.
JWT Decoder
Decode JSON Web Tokens instantly and offline.
Hash Generator
Generate MD5, SHA-1, SHA-256, and SHA-512 hashes locally.
Password Generator
Generate strong, random passwords locally.
UUID Generator
Generate secure v4 UUIDs.
RegExp Tester
Test regular expressions and inspect matches locally.
Unix Timestamp Converter
Convert Unix epoch timestamps to and from human dates.
URL Encoder
Safely encode or decode URL parameters.
QR Code Generator
Create customizable QR codes and export as SVG or PNG.
Text Diff / Compare
Side-by-side or unified line/character diff comparison tool.
CSS Gradient Generator
Design linear and radial CSS gradients with live preview.
Why none of these tools have a server
Most “online” developer tools are a form that posts your input to somebody’s backend, formats it there, and posts the result back. That design is invisible in the UI and it is the whole problem: the moment you paste a production JWT into a decoder, that token exists in a log file you have never seen, on a host you cannot name, under a retention policy you never agreed to.
Every tool on this site is built the other way round. The page you load is static HTML and JavaScript, delivered from a CDN and then done talking to the network. The formatting, hashing, encoding and parsing all happen in the tab you already have open, using the same JavaScript engine that renders this paragraph. There is no API call behind the “Format” button because there is no API — the site has no backend to run one on.
That constraint shapes what is here. A tool that genuinely needs a server — sending mail, querying a live database, calling a paid third party — does not get built, and the 979 that exist are things a browser can do on its own. Modern browsers can do more than most people expect: SHA-256 and AES come from the built-in Web Crypto API, image resizing and format conversion run on a canvas, PDFs are assembled in memory, and OCR runs a WebAssembly build of Tesseract that downloads once and then works offline.
Your input is not a disclosure
Pasting a config file, an API response or a token into a tool here does not hand it to a third party, because the request that would carry it is never made. That is a structural property of the page, not a promise in a privacy policy.
You can verify it in ten seconds
Open your browser's developer tools, select the Network panel, clear it, then use any tool on this site. Requests do appear — POSTs to cloudflareinsights.com/cdn-cgi/rum, which is Cloudflare's page-performance analytics, and on a reload a script and a POST to /cdn-cgi/challenge-platform/ for its bot detection. Open any one of them and read the payload: the page URL, the referrer, load timings. Never the contents of the box. That is the check worth running on any site — not whether requests fire, but whether your input is inside them.
It keeps working with no network
A service worker caches pages you visit, so a tool you have opened once still runs on a plane, on hotel Wi-Fi that has stopped resolving DNS, or inside a network that blocks the domain outright.
There is no round trip to wait for
No request means no latency floor. Formatting a large JSON document is bounded by your CPU rather than by a queue on somebody else's box, and the tool responds while you type instead of after you submit.
Where the approach runs out
It is a real trade-off, so here is the other side. Very large files are limited by the memory of the tab, not by a machine with 64 GB — a few hundred megabytes is a realistic ceiling, and a browser tab will simply die past it rather than warn you first. Nothing syncs between your devices, because nothing is stored anywhere but your own browser; clearing site data clears your pinned tools with it. A handful of tools depend on browser APIs that are still uneven across engines, and they say so on their own pages rather than failing silently. And a client-side tool cannot do anything that fundamentally requires a network peer — there is no port scanner here, and What is my IP is upfront about needing an external service to answer at all.
The longer version, including the build and the threat model, is in How it’s built & privacy.
Browse by category
Ten categories, 979 tools. Each card links to that section of the full directory.
Formatters & Validators (42)
Clean, format, validate, and compare your raw code and text structures.
Converters (192)
Transform data between formats — JSON, YAML, CSV, XML, and more.
Encoders & Decoders (44)
Safely encode, decode, and convert data formats without leakage.
Cryptography & Security (36)
Client-side hashing, token decoding, and secure generation.
Generators (71)
Generate identifiers, placeholder data, and assets on demand.
Text Tools (121)
Manipulate, clean, count, and reshape text instantly.
Developer Utilities (134)
Network math, syntax parsers, and everyday developer helpers.
Web & SEO (50)
Generate meta tags, social cards, and marketing URLs for the web.
Design & CSS (134)
Client-side utilities for frontend styling and color.
Calculators (155)
Fast, precise calculators for everyday math and dates.
Latest guides
69 written guides on the things these tools are for — what the formats mean, where they bite, and which tool to reach for.
What Online Tools Do With Your Data: We Measured 28
We drove 28 popular online tools in a real browser with a marked payload and recorded every request. Paste-based tools uploaded 2 times in 15; file-based tools 3 times in 5. Every privacy claim we found was true. Here is the data, and how to check any tool yourself.
Terraform HCL Explained: Blocks, Arguments, Expressions, and Common Patterns
HashiCorp Configuration Language powers Terraform infrastructure-as-code. This guide explains HCL syntax, block types, expressions, and the patterns you'll use in every Terraform project.
The 50/30/20 Budget Rule: How to Actually Build a Budget That Sticks
Most budgets fail because they're too complicated or too strict. The 50/30/20 rule is simple enough to follow but structured enough to make real progress on savings and debt.
Character Limits, Hashtags, and Algorithms: A Developer's Guide to Social Media Content
Social media platforms have wildly different technical constraints. This guide covers the character limits, image sizes, and optimization tips that matter for each major platform.
Descriptive Statistics Every Developer Should Know: Mean, Median, Regression, and More
Most developers learn statistics on the job, usually when it's urgent. This guide covers the descriptive statistics that actually come up in real data analysis work.
Complex Numbers Explained: From i to Fourier Transforms
Complex numbers appear in signal processing, quantum mechanics, and electrical engineering. Here's an approachable explanation of the math — from basic arithmetic to polar form.
Frequently Asked Questions
- What is ZeroServer.tools?
- ZeroServer.tools is a free collection of 979 developer utilities — JSON formatter, Base64, password generator, hashing tools, converters, and more — that all run entirely in your browser. There is no backend: no server, no account, and no upload step.
- Is ZeroServer.tools free to use?
- Yes. Every tool is completely free, with no account, no paywall, no trial, and no usage limits. There is nothing to sign up for, because there is nothing to sign in to.
- Does ZeroServer.tools store or upload my data?
- No. Every tool processes your input in JavaScript inside your own tab, so it never leaves your device. You do not have to take that on trust: open your browser's developer tools, switch to the Network panel, and use any tool on the site — nothing carrying your input is ever sent, because there is no endpoint to send it to. Two things do appear, and neither carries a byte of what you typed. On page load, a script and a POST to /cdn-cgi/challenge-platform/: our CDN's bot-detection analytics, added at the edge. And both on load and again while you type, POSTs to cloudflareinsights.com/cdn-cgi/rum: that is Cloudflare's page-performance analytics, and its payload is the page URL, the referrer and load timings. So the panel is not empty while you work — it is simply that none of what is in it is yours.
- How many tools are available, and how are they organised?
- There are 979 tools across ten categories: Formatters & Validators, Converters, Encoders & Decoders, Cryptography & Security, Generators, Text Tools, Developer Utilities, Web & SEO, Design & CSS, and Calculators. The full index lives at /tools/, and the sidebar search matches on tool names and keywords.
- Do the tools work offline?
- Most of them, yes. The site registers a service worker on your first visit, so pages you have already opened keep working with no network at all — useful on a plane, or on a locked-down network. Tools that download a model or a font on demand (OCR and the AI tools) are the exception and need one online run first.
- Can I use these tools on work data?
- That is what the client-side design is for — the input never reaches a third party, so pasting a config file or a token does not create a disclosure the way it would on a tool that posts to a server. Check your own organisation's policy, and prefer the offline check above if you need to prove it.