How to decode a Base64 string

When you receive a Base64 string — from an API response, a JWT payload, a data URI, or a debugging session — you often need to decode it to see the original content. This guide shows how to decode any Base64 string to plain text in seconds, handle URL-safe variants, and deal with missing padding.

Step-by-step guide

1. Copy the Base64 string: Copy the Base64-encoded value. It may end with = or == (padding), or be URL-safe with - and _ characters.
2. Select decode mode: Open quickhelp.dev/base64 and select 'decode' in the mode selector.
3. Choose the charset: If your string contains - or _, select 'url-safe'. Otherwise keep 'standard'. The tool also auto-detects url-safe characters.
4. Read the output: The decoded plain text appears instantly. If the input is not valid Base64, the 'valid' field is false and an error message explains the problem.

Frequently asked questions

What if the decoded output is garbled?

The input is binary data, not UTF-8 text — for example, an encoded image or binary file. The decoder always outputs UTF-8, so binary content will look garbled. For image data URIs, use the Image Converter instead.

What if I get 'Invalid Base64 input'?

The string contains characters outside the Base64 alphabet, or it is incomplete. Check for truncation, and try toggling between standard and url-safe charset if it contains - or _.