Free Websites Every Developer Should Bookmark

Free Websites Every Developer Should Bookmark

The short answer: a handful of free websites — MDN Web Docs, Can I Use, DevDocs, Regex101, a JSON formatter, and Excalidraw — cover most of what a developer looks up every single day, and bookmarking them saves far more time than any single paid subscription.

Updated for 2026. Links and free-tier details change — verify before relying on any resource for a deadline.

None of these sites do anything flashy. They are reference material, formatters, and quick utilities — the kind of tab you open ten times a day without thinking about it. That's exactly why they belong in a bookmarks bar rather than a search history you have to reconstruct every time.

Documentation and Reference

Reference sites answer "what does this actually do" questions faster than a search engine, because they're structured for lookup rather than discovery.

MDN Web Docs — the standard reference for HTML, CSS, JavaScript, and Web APIs, maintained collaboratively by browser vendors and the open web community. Every page includes a browser compatibility table so you don't need a separate tool for that check. Best for: looking up exact syntax and behavior of any core web platform feature. Status: Free.

Can I Use — a browser support matrix showing which CSS properties, JavaScript APIs, and HTML features work in which browsers and versions, with usage-percentage data to help you judge real-world risk. Best for: deciding whether a feature is safe to ship without a polyfill. Status: Free.

DevDocs — an aggregator that combines dozens of languages' and frameworks' official documentation into one fast, searchable interface with offline support. Best for: developers who bounce between several stacks and want one search habit instead of five bookmarked docs sites. Status: Free.

TypeScript Handbook — the official TypeScript documentation, covering everything from basic types to advanced generics and utility types with runnable examples. Best for: understanding a TypeScript error message or feature you haven't used before. Status: Free.

HTTP Status Dogs / httpstatuses.com — quick reference for what an HTTP status code actually means in context, beyond the bare numeric list. Best for: debugging an API response without memorizing the full status code spec. Status: Free.

DevDocs and MDN cover the platform itself, but framework-specific documentation still deserves its own bookmarks. The React documentation, Next.js documentation, and Tailwind CSS documentation are each maintained directly by their respective teams and tend to be more current and accurate than any third-party tutorial covering the same framework. Best for: checking the exact current API of a framework you use daily rather than trusting a blog post that may reference an older version. Status: Free.

Formatters and Validators

These sites take messy or malformed data and make it readable, or confirm it's valid before you ship it.

JSONLint — validates and pretty-prints JSON, flagging the exact character where a malformed payload breaks. Best for: debugging an API response that looks fine at a glance but fails to parse. Status: Free.

Regex101 — builds and tests regular expressions against real sample text with a live, plain-language explanation of each part of the pattern, plus a debugger for tracing exactly how a match happens. Best for: writing or debugging a regex you don't want to get wrong in production. Status: Free with optional account for saved patterns.

JWT.io — decodes and inspects JSON Web Tokens, showing the header, payload, and signature verification status without needing to write a decoding script yourself. Best for: debugging authentication issues involving JWTs. Status: Free.

Prettier Playground — the official in-browser version of the Prettier code formatter, useful for testing formatting rules before committing them to a project config. Best for: previewing how a formatting rule change will affect your codebase. Status: Free.

Diffchecker — compares two blocks of text, code, or entire files and highlights exactly what changed between them, which is faster than manually scanning two versions side by side. Best for: spotting an unexpected change between two versions of a config file or a piece of code someone else sent you. Status: Free with a paid tier for larger files.

Base64 Guru / base64decode.org — encodes and decodes Base64 strings directly in the browser, useful when debugging an encoded token, image data URI, or API payload without writing a throwaway script. Best for: quickly inspecting what a Base64-encoded value actually contains. Status: Free.

Design and Diagramming

Not every developer task is code — these tools cover the whiteboard-adjacent work of planning and communicating a design before it's built.

Excalidraw — a free, open-source virtual whiteboard for sketching diagrams, architecture sketches, and wireframes with a deliberately hand-drawn look that keeps early-stage sketches from looking falsely finished. Best for: quick system diagrams and architecture sketches shared with a team. Status: Free.

Coolors — generates and locks color palettes quickly, with an option to check contrast ratios for accessibility. Best for: picking a UI color scheme without a design background. Status: Freemium.

Google Fonts — a free, open-license library of web fonts with direct embed code for any project. Best for: adding typography to a project without a licensing question to resolve. Status: Free.

Figma (free tier) — a browser-based design tool that has become the de facto standard for handing off UI designs between designers and developers, with a free tier covering personal projects and small teams. Best for: inspecting a designer's actual spacing, color, and font values directly from a shared design file instead of guessing from a screenshot. Status: Freemium.

Code Playgrounds and Sharing

Sometimes you need to demonstrate a bug or a idea without spinning up a full local project.

CodePen — a browser-based playground for HTML, CSS, and JavaScript, ideal for sharing a small, runnable demo or reproducing a front-end bug in isolation. Best for: sharing a minimal reproduction of a CSS or JS issue. Status: Freemium.

StackBlitz — spins up a full, runnable development environment in the browser instantly, including frameworks like React, Vue, and Angular, with no local setup. Best for: sharing a working code example that needs more than a single HTML file. Status: Free.

TypeScript Playground — the official in-browser TypeScript compiler, letting you test type behavior and see compiled JavaScript output side by side. Best for: understanding how a specific TypeScript feature compiles or behaves. Status: Free.

Quick Reference Table

Testing and Accessibility

Before shipping anything user-facing, a small set of testing and accessibility sites catch problems a normal browser preview won't surface.

WebAIM WAVE — a free accessibility evaluation tool that scans a live page or pasted HTML and flags contrast issues, missing alt text, and structural problems for screen readers. Best for: a quick accessibility pass before shipping a page, without installing a browser extension. Status: Free.

WebPageTest — runs a real page load from actual browser instances in various locations and network conditions, returning a detailed waterfall of every request. Best for: diagnosing why a page loads slowly on a connection that doesn't match your own fast office wifi. Status: Free.

Lighthouse (via PageSpeed Insights) — Google's automated audit for performance, accessibility, SEO, and best practices, available both as a website and built into Chrome DevTools. Best for: a fast, standardized score to track before and after a performance change. Status: Free.

BrowserStack (free tier) — cross-browser and cross-device testing infrastructure, with a limited free tier for open-source projects and short manual testing sessions. Best for: checking a layout on a real Safari or older Android device you don't personally own. Status: Freemium.

APIs and Data for Practice Projects

A portfolio project needs real data to feel credible, and these sites remove the need to build your own backend just to have something to fetch.

JSONPlaceholder — a free fake REST API returning realistic placeholder data for posts, users, and comments, useful for testing frontend code against a real HTTP response shape. Best for: building or testing a frontend before a real backend exists. Status: Free.

Postman Public API Network — a searchable directory of publicly documented APIs with ready-made request collections you can fork and test immediately. Best for: exploring what a third-party API actually returns before writing integration code. Status: Free.

OpenWeatherMap — a free-tier weather API commonly used in tutorials and small projects because its documentation is clear and its free tier is genuinely sufficient for a demo project. Best for: a beginner-friendly first API integration project. Status: Freemium.

Comparing the Categories

Different tasks call for a different type of site, and it helps to think of your bookmarks bar as covering distinct jobs rather than one undifferentiated pile of links.

Thinking in terms of the job, rather than the specific site name, makes it easier to slot in a replacement later if a particular tool changes or shuts down — you're preserving the category of habit, not just a single bookmark.

Building a Bookmark System That Actually Works

A flat, unorganized bookmarks bar with forty items is arguably worse than no bookmarks at all, because it forces you to visually scan past dozens of items you rarely use to find the one you need right now. A better structure groups bookmarks into folders by task type — documentation, formatters, playgrounds, testing — with only the handful you use most placed directly on the visible bar, and everything else one click deeper in a folder.

Browser bookmark folders sync automatically across devices when you're signed into your browser account, which matters more than it initially seems: the tool you desperately need mid-debugging session on a work laptop should be exactly as accessible on a personal machine later, without having to remember and retype a URL. If your browser supports keyboard-triggered bookmark search — most modern browsers do, often bound to a keyboard shortcut that searches bookmark titles — learning that shortcut removes the need to visually scan a bar at all, which scales far better as your list grows.

It's also worth distinguishing bookmarks you use standalone from ones better triggered contextually. A regex tester or JSON formatter is something you reach for in the middle of another task, so binding it to a fast keyboard-driven search matters more than for a reference site like MDN, which you might more often navigate to directly by typing a few characters of its name into the address bar, since most browsers learn frequently visited domains and autocomplete them after just a couple of keystrokes.

How to Actually Use This List

Bookmark five, not twenty. The sites that earn a permanent spot in your bar are the ones tied to something you look up weekly, not the ones that seemed useful the day you found this list.

Group your bookmarks by task type rather than alphabetically — documentation together, formatters together, playgrounds together — so muscle memory takes over instead of scanning a long flat list every time.

Re-test any tool you haven't opened in a few months before trusting it under deadline pressure. Free web tools occasionally change their interface, add a paywall on a previously free feature, or go offline entirely, and the worst time to discover that is mid-task.

Consider keeping a short personal note, even just a single line in a notes app, next to any tool whose free tier has specific limits you need to remember — a file size cap, a rate limit, a maximum number of saved projects. Re-discovering a limit the hard way, mid-deadline, is a completely avoidable frustration if you wrote it down the first time you hit it.

The Four Mistakes

Bookmarking everything and using nothing. A bookmarks bar with forty tabs is functionally the same as no bookmarks at all. Keep the list short enough that you actually recognize each icon at a glance.

Relying on a single site for browser compatibility instead of testing directly. Can I Use is a strong first check, but real device testing still catches edge cases that a compatibility table can't fully capture, especially on older or less common browsers.

Trusting a JSON or regex tool with sensitive production data. Formatters and testers are convenient, but paste only synthetic or already-public data into a third-party site — never real credentials, tokens, or customer data.

Forgetting that documentation sites version their content. MDN and framework docs usually show the current stable version by default; if you're on an older version of a library, check that the documentation page you're reading actually matches your installed version before trusting a code example.

Relying entirely on browser search history instead of deliberate bookmarks. Search history feels like it accomplishes the same thing as a bookmark, since you can technically retype a past search and find the site again. In practice, history is unreliable for anything you need under time pressure — it can be cleared, it mixes in unrelated searches, and it doesn't survive a fresh browser profile or a new machine the way a synced bookmark does. Treat history as a discovery mechanism, not a storage mechanism for the tools you actually depend on.

When a Bookmarked Site Isn't Enough

Not every problem a bookmarked web tool solves stays solved by that tool forever. As a project grows, some of these browser-based utilities are worth graduating away from in favor of an integrated, local equivalent — a linter and formatter configured directly in your editor and CI pipeline, for instance, catches issues before you ever need to manually paste code into a web-based formatter. Treat the web tools in this list as excellent for quick, one-off checks and for situations where installing a local tool isn't worth the setup cost, but recognize the point at which a repeated manual step is better automated into your actual development workflow.

A concrete example: Regex101 is genuinely the right tool for building and debugging a single regular expression interactively. But if your project relies on a library of regular expressions used repeatedly across the codebase, those patterns belong in version-controlled code with actual unit tests, not as a one-off pasted into a web tool and then manually copied into a file. The web tool is where you develop the pattern; the codebase is where it should permanently live once it's correct.

Keeping This List Current for Yourself

The specific sites named in this article are accurate as of this writing, but the underlying categories — documentation, formatters, diagramming, playgrounds, testing, and practice APIs — are more durable than any individual tool within them. If a specific site listed here ever changes ownership, adds a paywall to a previously free feature, or shuts down, the right response is to find a replacement within the same category rather than assuming the entire category of tool is no longer useful.

A practical habit worth adopting: once or twice a year, open your own bookmarks folder for developer tools and actually click through each one. Confirm it still works the way you remember, still has the free tier you're relying on, and still solves the problem faster than a general search would. Removing a stale bookmark takes seconds; discovering it's broken mid-task, under deadline pressure, costs considerably more.

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