Base64 Standard Detector

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Inspect a Base64 string to see which alphabet it uses, whether padding is present, and whether it is wrapped in a data URL.

Last updated: May 17, 2026•Author: Mateo Díaz•Reviewed by: Riley Williams

In-browser

Detect standard Base64, Base64URL, padding, and data URL details

Input

Characters: 16Words: 1Sentences: 0Lines: 1

Output

Characters: 0Words: 0Sentences: 0Lines: 0

What is a Base64 standard detector?

A Base64 standard detector checks whether a string uses standard Base64, URL-safe Base64URL, padding, or a data URL wrapper. It also reports validity and decoded size.

How to use it

Paste the Base64 string.
Review alphabet, padding, data URL, and decoded size details.
Normalize or repair the value if needed.

Example

Input: SGVsbG8td29ybGQ_

Output: Base64URL-style characters detected.

Common mistakes

Standard Base64 uses + and /; Base64URL uses - and _.
Padding is optional in some systems but required in others.
A data URL has metadata before the Base64 payload.

Related tools

Clean the value with Base64 normalize.
Check strict validity with the Base64 validator.
Fix common issues with Repair malformed Base64.

Privacy and security

Detection runs locally in your browser.

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