EML Viewer
A fast, mobile-first, single-file email viewer. Drag & drop an .eml and
read the message — headers, body, and attachments — with an SPF / DKIM /
DMARC authentication readout up top. It's a viewer, not a client — no
accounts, no sending, no uploads. Everything runs locally in your browser.
🔗 Live: https://eml-viewer.us/
Part of the File Viewer family — HTML, Markdown,
ePUB, PDF, Data, DOCX, Sheets, and EML each have their own dedicated viewer.
Use the ☰ menu in the header to jump between them.
Features
- 🔐 SPF / DKIM / DMARC readout — parsed from the message's
Authentication-Results, Received-SPF, and DKIM-Signature headers and
shown as clear pass / fail / none badges with the signing domain and
selector. (Reads what the receiving server recorded — no live DNS lookups.)
- 📇 Header card — From, To, Cc, Subject, Date, Reply-To, cleanly formatted
(RFC 2047 encoded-words decoded, including emoji).
- 📄 Body — HTML parts render in a sandboxed iframe with remote images
blocked for privacy (no tracking pixels phone home); plain-text parts render
with clickable links.
- 📎 Attachments — listed with type and size, each downloadable (decoded
locally to a
data: URL — nothing leaves your device).
</> Source view — one tap shows the raw .eml.- ☰ Family menu · 🫥 auto-hiding header · 🎨 pick any background color.
- 🪶 One file, no build —
index.html is self-contained and works offline,
even from file://.
- 📊 Privacy-friendly analytics — self-hosted, cookieless
Plausible; your messages never leave your device.
Supported file types
.eml .mbox .emlx
Outlook .msg (compound-binary) isn't parsed yet — the viewer detects it and
asks you to Save As → .eml first. (Planned.)
Quick start
Just open it. Download index.html, double-click it — no
server, no build, no internet needed.
python3 -m http.server 8080 # then open http://localhost:8080
Deploy to Cloudflare Pages
Connect the repo (Workers & Pages → Create → Pages → Connect to Git),
framework preset None, build command blank, output directory /. The
_headers file applies a strict CSP automatically. Add the custom
domain eml-viewer.us under the project's Custom domains tab.
How it works
Everything is in index.html: a small, dependency-free MIME parser
(headers, multipart, base64 / quoted-printable, charset via TextDecoder,
RFC 2047 encoded-words) plus the auth-header analysis, both written for this
project. highlight.js is inlined
only to colorize the raw-source view.
HTML message bodies render inside a sandboxed <iframe> whose own
Content-Security-Policy allows only inline styles and data: images — so
scripts never run and remote images/trackers are blocked. Attachments are
decoded in memory and offered as data: downloads. The viewer's own CSP stays
strict (default-src 'none', no external assets).
Note: SPF/DKIM/DMARC results are read from the headers the receiving mail
server added — this is a viewer, not a validator, and performs no live DNS or
cryptographic verification.
Credits
The MIME parser and auth analysis are original to this project. Envelope icon
by the author. Analytics by Plausible.
License
MIT © 2026 Michal Ferber, aka TechGuyWithABeard. Bundled
components retain their own licenses — see LICENSE and
Credits.
