Email MIME Structure Viewer
Explore the MIME parts inside an EML email. Inspect content types, charsets and encodings, then download decoded parts or a structure JSON.
Drop your EML file here
See how the message, alternative bodies and attachments fit together.
.eml files up to 25 MB · No upload requiredOpening your email…
How to inspect an email's MIME structure
MIME describes how an email combines body text, HTML, inline resources and attachments. This viewer shows the recovered part tree in source order, so you can connect a displayed message with the parts that produced it.
- Open an EML file or the multipart sample email.
- Select a part to inspect its headers, declared content type, charset, encoding and decoded size.
- Download a decoded leaf part or the structure JSON. Switch to the email tabs for the readable message.
A MIME tree from the sample email
The fictional studio-visit email contains two versions of the body and one text attachment. Its tree below mirrors the structure you can inspect with the sample button. The outer container groups the body and attachment; the inner container offers plain text and HTML as alternatives.
Structure of studio-visit.eml
multipart/mixed
├── multipart/alternative
│ ├── text/plain; charset=UTF-8
│ │ Content-Transfer-Encoding: 8bit
│ └── text/html; charset=UTF-8
│ Content-Transfer-Encoding: 8bit
└── text/plain; name="visit-details.txt"
Content-Disposition: attachment
Content-Transfer-Encoding: base64Mixed, alternative and related parts
These types explain the intended relationship between parts. A real message may nest them, use other MIME types or contain malformed declarations. The viewer shows what its parser recovered; it is not a MIME compliance validator and does not certify that every mail client will interpret the file identically.
| MIME container | Typical purpose | How to interpret it |
|---|---|---|
| multipart/mixed | A body and additional independent parts. | Look for attached documents or other files beside the message. |
| multipart/alternative | Different representations of the same content. | Plain text and HTML are common alternatives, not two separate emails. |
| multipart/related | A body and resources used by that body. | Content-ID can connect an inline image to a cid: reference in HTML. |
Content type, charset and transfer encoding
Content-Type declares the media type, such as text/html or image/png. A charset parameter tells a text reader how to interpret its bytes. Content-Transfer-Encoding describes how those bytes were represented for email transport, commonly as base64, quoted-printable or unencoded 8bit data.
Content-Disposition can mark a part as an attachment or inline content, often with a filename. Content-ID can identify an inline resource referenced from another part. Select the part to inspect these fields together rather than assuming that a filename extension is the complete description.
A decoded size refers to the part after transfer decoding. It can differ from the size of the encoded text in the EML. The declared charset is a separate step from transfer decoding; downloading a raw part does not automatically turn it into a UTF-8 text document.
Decoded part downloads and the JSON manifest
A leaf download contains the original part bytes after transfer decoding. The download is not sanitized. For example, an HTML part can retain content removed from the safe email preview. The structure view does not execute that HTML; use the EML to HTML converter when you want a cleaned reading copy.
The JSON manifest records structure, headers and part metadata without including the body bytes. It is useful for comparing how messages are assembled, while the original EML remains the source needed to reproduce the complete content.
An attached message/rfc822 is kept as one downloadable part. Download that attached email and open it separately to inspect its own nested structure. The viewer accepts up to 25 MB, 1,000 MIME parts and 30 nesting levels; exceeding a limit produces an error instead of a truncated tree.
Email MIME viewer questions
What does multipart/alternative mean?
It groups alternative versions of the same content, often plain text and HTML. multipart/mixed commonly combines a body with attachments; multipart/related groups a body with associated inline resources.
Does this validate MIME compliance?
No. It displays the structure recovered by the parser, which can tolerate some malformed messages. It is not a standards validator or an authenticity check.
Are attached EML messages expanded?
An attached message/rfc822 remains one downloadable part. Download it and open it separately to inspect its internal MIME structure.
Are decoded parts sanitized?
No. Decoded part downloads contain original bytes after transfer decoding, and are labeled accordingly. The email preview is sanitized separately. MIME part HTML is not executed in the structure view.
What are the limits?
Files are limited to 25 MB, with up to 1,000 MIME parts and 30 nesting levels. An input exceeding those limits produces an error rather than a truncated structure.
Does my data leave my device?
Your selected files and pasted text are processed in your browser, without being uploaded to EMLKit. Remove the input or leave the page to clear the current workspace. Ordinary page requests still reach the site host. Read about file handling.