Encoding Tools Every Developer Needs
Base64, URL encoding, JSON and slugs — four everyday conversions, why each shows both directions at once, and the encoding choice that actually matters.
The tools in this guide
All free, no signup. Each one has a printable sheet too.
- Base64 Encoder & DecoderPaste text or Base64 and get both forms at once. Runs entirely in your browser — nothing is uploaded.
- URL Encoder & DecoderBoth directions at once, so you never pick the wrong one - and it encodes the component-safe way, which is the one you almost always want.
- JSON Formatter & ValidatorPaste JSON and get it indented and minified at once - and if it is broken, the parser's own error with the line and column.
- URL Slug GeneratorTurns a headline into a clean URL slug - and shows you the shortened version too, because the best slug is usually not the whole title.
These are the conversions you do a dozen times a week and never quite memorise. Four tools, all running entirely in your browser — which is the part that matters, because the strings you paste into an encoder are frequently tokens, payloads or customer data.
Nothing here is uploaded. That is a deliberate design choice, not a marketing line.
Both directions, always
Every tool in this group shows both directions at once, and that is a considered decision rather than a shortcut.
The reason: with a mode dropdown, the most common error is running the wrong direction and getting plausible-looking garbage back. Base64 of Base64 is still valid Base64. Double-encoding a URL produces a working-looking string that fails somewhere much later. Showing both removes an entire class of mistake, because the right answer is always on screen.
Base64
The Base64 Encoder & Decoder takes text or Base64 and gives you both forms together.
Worth remembering that Base64 is an encoding, not encryption — it is trivially reversible, which is exactly why this tool can do it in your browser with no key. Anything sensitive that is merely Base64'd is not protected in any sense.
URL encoding, and the choice that matters
The URL Encoder & Decoder does both directions, and it encodes the component-safe way, which is the one you almost always want.
That distinction is the real content of this tool. There are two encoding functions in most
languages: one that preserves the characters that structure a URL (/, ?, &, =) and one that
escapes them too. If you are encoding a whole URL, you want the first. If you are encoding a
value that goes inside a URL — a query parameter, a path segment — you want the second, because
otherwise an & in your value silently becomes a parameter separator.
The second case is far more common, and it is the one that produces bugs that look like data corruption. Component-safe is the sensible default.
JSON
The JSON Formatter & Validator gives indented and minified at once — and when the input is broken, the parser's own error with the line and column.
That last part is what makes it a debugging tool rather than a pretty-printer. "Invalid JSON" tells you nothing; a line and column tells you it is the trailing comma on line 41.
Slugs
The URL Slug Generator turns a headline into a clean slug and shows the shortened version too, because the best slug is usually not the whole title.
A slug generated from a full headline is long, carries filler words, and ages badly when the headline gets edited. The shortened form is usually the better URL.
The short version
- Both directions at once — it removes the wrong-direction error entirely.
- Base64 is encoding, not encryption.
- Component-safe URL encoding is the default you want for anything going inside a URL.
- A JSON error with a line and column is worth more than "invalid".
- Shorter slugs age better than headline-length ones.
- All of it stays in your browser.
Each has a printable, though for this group the browser-only guarantee is the feature — these are the tools you reach for with a production token in your clipboard.
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