Base62 decoder.

Base62 writes a number with all 62 letters and digits, 0 to 9, A to Z then a to z, and no symbols. It is the densest alphabet that needs no escaping anywhere: not in a URL, a file name, a JSON string or a shell. The tool treats the input bytes as one big number and writes that.

The bytes are read as one integer, big end first, and written in base 62 by repeated division. Each character carries about 5.95 bits, so the output is about 34% larger than the input, close to Base64. Leading zero bytes are kept as leading 0 characters. There is no padding.

URL shorteners (bit.ly's slugs), short unique ids, invite and referral codes, session and API tokens, and anywhere a 64-bit id has to become an 11-character string that fits a URL untouched.

Yes: letters and digits only, nothing to escape.

Nearly as short as Base64 with none of its symbols, which is why web ids use it; but case-sensitive, so a person transcribing it can slip, and converted as one number, so it is slow on anything big. Base58 drops the look-alike characters for the same job; Base36 drops case; Base64 streams.

No. Base62 is an encoding, not encryption: it changes how bytes are written, not who can read them, and anyone can decode it with no key. Encrypt first (AES, age, a library's sealed box) when the content needs protecting, then encode the ciphertext if it has to travel as text.

Paste the Base62 and the text appears as you type; the status line says how many characters became how many bytes. Spaces and line breaks are ignored, so a wrapped value from an email or a config file pastes as it is. Press Swap to encode the result again.

The decoder gives you the bytes as UTF-8 text when they are text. When they aren't, an image or a PDF for instance, it still shows them, with replacement characters where the bytes aren't valid UTF-8, and the status line says so. Use Base62 to file to download the bytes as they are instead.

Base62 uses 0 to 9, A to Z and a to z, and the error names the first character that isn't among them. Check for a stray quote, a trailing comma or a prefix from the surrounding code. Spaces and line breaks are dropped for you.

Nothing leaves your browser. The text is read into memory on your machine and the encoding is computed there, in plain JavaScript; the page makes no request with it. Load the page, go offline and it keeps working.

No. The Base62 decoder is free and opens without a sign-in, an account or an install.

Nothing. The Base62 decoder holds your input in the page's memory, so closing or reloading the tab clears it, and it saves nothing in this browser.

It takes digits and letters in either case, and reads a leading 0 as a zero byte. Anything else stops with a message naming the first character it can't read.

Yes: drop a text file that holds the Base62 on the input. The file is read as text and decoded, so a saved encoding doesn't need pasting.

Press Swap once there is a result and the same tool becomes the Base62 encoder, with the decoded text moved into the input.

Closest to the Base62 decoder: Base62 encoder, Base62 to file, File to Base62, Base58 decoder. Each opens on its own page, free and in the browser.

The Base62 decoder is one of 32 in its group. The group's page, /tools/encoding, lists them all.

The tool is free. Its interface is built from shadcn.io's own components (Button, Input, Slider and the rest of the registry under /ui), which come in React, Vue, Svelte and Solid. Pro adds the blocks and templates for the product around it.