How do I decode a Base64 string?

Paste it into the box and the decoded UTF-8 text appears instantly. The tool maps each group of 4 Base64 characters back to 3 bytes and decodes them as text.

Does it handle URL-safe Base64?

Yes. The decoder accepts both the standard +/ alphabet and the URL-safe -_ alphabet, converting - to + and _ to / before decoding.

What if my Base64 is missing its = padding?

The decoder restores padding automatically based on the string length, so unpadded Base64 (common in JWTs and URLs) still decodes correctly.

Why do I get an invalid input error?

The string contains characters that are not valid Base64, or its length leaves a single leftover character that cannot form a byte. Stray spaces, truncation, or non-Base64 text are the usual causes. Invalid UTF-8 byte sequences are also flagged.

Can it decode Base64 that is not text, like an image?

This tool decodes the bytes and shows them as UTF-8 text, so binary payloads such as images will not be readable here. For images, use a Base64-to-image tool instead.

No. Decoding runs entirely in your browser with built-in APIs — nothing is transmitted anywhere.

What is the Base64 Decoder?

Free Base64 decoder that converts standard or URL-safe Base64 back into readable UTF-8 text, restoring missing padding automatically. Runs entirely in your browser — nothing is uploaded. It runs free in your browser on Gera Tools, with nothing uploaded.

Base64 Decoder — Gera Tools

Name: Base64 Decoder
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

Base64 decoder

Turn a Base64 string back into readable text. The decoder accepts both the standard and URL-safe alphabets, fixes missing padding for you, and decodes the bytes as UTF-8 — useful for inspecting JWT payloads, data URIs, config values and email headers.

How it works

First the tool normalises the input: URL-safe characters - and _ are converted back to + and /, and any missing = padding is restored so the length is a multiple of 4. It then uses the browser’s built-in atob to turn each group of 4 characters into 3 bytes, and decodes those bytes with a strict UTF-8 decoder. If the bytes are not valid UTF-8, or the length is malformed, it reports an error rather than returning garbage.

Example

Decoding SGVsbG8sIEdlcmEgVG9vbHMh:

SGVsbG8sIEdlcmEgVG9vbHMh → Hello, Gera Tools!

Base64	Decoded text
`R2VyYQ==`	`Gera`
`SGk=`	`Hi`

To encode in the first place, use the Base64 encoder. All decoding happens locally in your browser — nothing is uploaded.

When you actually need a Base64 decoder

Base64 is not encryption — it is purely an encoding scheme designed to represent binary data using only printable ASCII characters. You encounter it constantly in real work without always recognising it:

JWT inspection: A JSON Web Token (JWT) is three Base64url-encoded sections separated by dots. The middle section (payload) is where claims like user ID, role, and expiry live. Paste the payload section here to read it — but remember, JWTs are signed, not encrypted. Anyone who holds the token can decode the payload; the signature only prevents tampering.
Email headers: MIME-encoded email headers use Base64 when subject lines or sender names contain non-ASCII characters. If you see =?UTF-8?B?...?= in a raw email header, the ... part is Base64.
Data URIs: Images and fonts embedded directly in HTML or CSS use the pattern data:image/png;base64,.... The Base64 portion after the comma is the raw image binary. This decoder will show garbled text for binary data because it decodes to UTF-8 — use a Base64-to-image tool if you need to view the image.
API responses and config values: Some APIs and configuration systems Base64-encode credentials, tokens, or serialised JSON for transport. If a config value “looks random” and ends in = or ==, try decoding it here.

Common errors and what they mean

Error	Likely cause
Invalid character	The string contains a space, newline, or non-Base64 character — strip it and try again
Odd length / incomplete byte	The Base64 is truncated; you may have copied only part of it
Invalid UTF-8 sequence	The decoded bytes are not text (image, audio, etc.) — this tool is text-only

Standard vs. URL-safe Base64

The standard Base64 alphabet uses + and / as the 62nd and 63rd characters. These are not safe in URLs (they have special URL meaning), so URL-safe Base64 replaces them with - and _. JWTs and OAuth tokens almost always use URL-safe Base64 and drop the = padding. This decoder handles both automatically.