Base64 Checker
Check if a string is valid Base64, decode it to text, or encode text to Base64. Supports whitespace and Base64URL (-_).
How to use
Paste your input, choose options, then run a check or conversion.
- Paste Base64 (or text to encode) into the input box.
- Optional: enable whitespace ignoring and Base64URL auto-detect.
- Click Check to validate, Decode to decode, or Encode to encode.
- Copy the output if needed.
FAQ
What does a Base64 checker do?
It validates whether a string is properly formatted Base64 and (optionally) attempts to decode it to confirm it’s actually decodable.
Why does my Base64 fail validation even though it looks close?
Common causes are invalid characters, incorrect padding (=), or a length that’s impossible for Base64 (for example length mod 4 equals 1).
Is missing padding (=) always invalid?
No. Many systems omit padding; disable “Require padding (=)” to accept valid unpadded Base64.
What is Base64URL and how is it different?
Base64URL replaces + and / with - and _, and often removes padding. Enable auto-detect or Base64URL decoding for these strings.
Can I decode binary data with this tool?
This tool decodes to UTF-8 text output. If the decoded bytes aren’t text, the result may look garbled.
Does whitespace/newlines break Base64?
Whitespace is common in copied logs or wrapped strings; enable “Ignore whitespace/newlines” to validate and decode correctly.
Is my input sent to a server?
No. The tool runs locally in your browser and doesn’t make network requests.
Continue your workflow
Browse related tools by task. Use the improved core tools for a consistent workspace with file import, downloads and clear validation errors.
Validation · Encode/decode · URL-safe/no padding
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Validate · Normalize/fix padding · UTF-8/hex preview
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