Nirmion
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Developer & Data

Base64 Decoder

Decode standard Base64 into strict UTF-8 text and reject malformed byte sequences.

  1. 01Runs in this browser
  2. 02Limits are explicit
  3. 03Copy or download output

Step 1

Set up the source

Paste standard Base64 text. Whitespace is ignored, but invalid alphabet, padding, and non-UTF-8 bytes are rejected.

Confirming the published workspace...

No black box

How this tool handles the input

The browser decodes Base64 to bytes, then decodes those bytes as UTF-8 with strict error handling.

Before you start

What you need

A standard Base64 value whose original content is UTF-8 text.

What you get

What the page gives back

Decoded text ready to review, copy, or download.

Keep in mind

Use the result responsibly

Binary files are not UTF-8 text and may be rejected. Decoding does not make untrusted content safe.

Practical uses

Where this tool earns its place

  1. Read a Base64-encoded configuration value.
  2. Verify an encoded API fixture.
  3. Recover known UTF-8 text from a standard Base64 field.

Verified data boundary

Source text stays on this page.

The published contract marks these tools as client-only processing. Nirmion uses the API only to confirm that this workspace is enabled in MySQL; source values and results are not sent to Flask.

Keep working

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