MIME Header Decoder
Use our free MIME header decoder to instantly parse and convert RFC 2047 encoded-word strings to readable text. Decode Base64 and QP headers online.
About MIME Header Decoder
The MIME Header Decoder converts encoded email header fields into plain, human-readable text. Internet email standards use RFC 2047 encoded-word syntax to represent non-ASCII characters in header fields like Subject, From, and To. This tool automatically parses the character set, encoding method, and payload to display the original text instantly.
Whether you are troubleshooting email delivery, analyzing raw headers from a suspicious message, or developing mail processing software, this decoder simplifies inspecting raw MIME data. The conversion runs entirely in your browser, ensuring your email contents remain private and secure on your device.
Key features
- Decodes RFC 2047 encoded-word format strings
- Supports Base64 and Quoted-Printable transfer encodings
- Handles multiple character sets including UTF-8 and ISO-8859-1
- Parses full header lines or isolated encoded segments
- Runs entirely in the browser without server transmission
- Provides quick one-click copying for decoded output
How to use MIME Header Decoder
- Paste the raw encoded MIME header into the input box.
- Click the Decode button to process the RFC 2047 text.
- View the translated, human-readable text in the output area.
- Click the Copy button to transfer the decoded string to your clipboard.
Who is it for?
- Software engineers debugging MIME parser implementations and mail generators
- Security analysts reviewing raw email headers for phishing investigations
- System administrators inspecting mail transfer agent (MTA) logs
- Email marketers verifying multi-language subject lines and sender names
Frequently asked questions
What is an RFC 2047 MIME encoded-word?
An RFC 2047 encoded-word is a standardized syntax used to embed non-ASCII text within email headers. It typically follows the format =?charset?encoding?encoded-text?=, where the encoding is either 'B' for Base64 or 'Q' for Quoted-Printable.
Which transfer encodings does this tool support?
The tool supports both standard RFC 2047 transfer encodings: 'B' (Base64) and 'Q' (Quoted-Printable), combined with character sets like UTF-8, ISO-8859-1, Windows-1252, and ASCII.
Is my email header data uploaded to a server?
No. The decoding process runs entirely client-side using JavaScript in your browser. None of your header data or text is sent to or stored on any remote server.
Can this tool handle multi-line or folded headers?
Yes. The decoder parses adjacent encoded words separated by whitespace or folding whitespace (FWS) in accordance with RFC 2047 specifications.
Is the MIME Header Decoder free to use?
Yes. This decoder is completely free to use online with no account registration or installation required.