Text Tools

Analyze Base64 Magic Bytes, MIME and Padding

Inspect Base64 alphabet, padding, decoded size and magic bytes to identify common encoded file formats locally before decoding or converting them.

File typeMIME typeDecoded sizeSignature / validity
Input

Base64 analyzer

Base64 Magic Bytes, MIME and Padding Analyzer

Inspect Base64 syntax, padding, decoded size, MIME clues and magic bytes to identify PNG, JPEG, PDF and other encoded formats without uploading the data.

How to use this tool

  1. Paste your text into the input field.
  2. Click the action button to process it.
  3. Copy or download the result.

Privacy

Processed locally; nothing is uploaded.

Raw byte workflow

Use Bytes to Image for Uint8Array, Buffer, decimal byte arrays and hexadecimal image data. The tool detects the image signature before previewing it.

Convert bytes to image
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Inspection details

Magic bytes, padding and Base64 format detection

Base64 text carries no universal filename, so reliable inspection combines several clues: a data-URL MIME declaration when present, Base64 syntax and padding, the estimated decoded byte count, and magic bytes from the decoded prefix. Those signals can identify many common files before a full preview is attempted.

Decoded size can be estimated from the Base64 length because four encoded characters normally represent three bytes. Padding characters at the end reduce the final byte count, while whitespace and surrounding wrappers should be removed before calculating the estimate.

Magic-byte checks

  • PNG: 89 50 4E 47
  • JPEG: FF D8 FF
  • PDF: 25 50 44 46 (%PDF)
  • ZIP-based files: 50 4B 03 04

Decoded-size estimate

  • Start from normalized Base64 length.
  • Every four Base64 characters encode up to three bytes.
  • Subtract bytes implied by one or two trailing = padding characters.
MIMEmagic bytespaddingdecoded bytesBase64URL
Related workflows

These links connect the current task with the closest reverse, inspection or format-specific workflow.

Base64 Decoder

Decode the payload after inspection when it may contain text, binary data or a file.

Base64 to PDF

Open the dedicated PDF workflow when the signature resolves to application/pdf.

Base64 to Image

Preview and download the payload when the decoded bytes identify a supported image.