# The HTML Report Is Too Big to Email — Shrink It, or Stop Attaching It
Canonical: https://commareports.com/fix/html-file-too-big-to-email
Published: 2026-09-07
> Gmail caps attachments at 25 MB, Outlook at 20, and a self-contained report blows past both. What is actually making the file large, how to cut it, and the delivery that has no cap.
# The report bounced: attachment too large
`Message exceeds the maximum size` — or worse, no bounce at all and a
recipient who never mentions it.
## The limits you are hitting
| Where | Cap |
| ------------------------------ | ---------------------------------------------- |
| Gmail | 25 MB (auto-switches to a Drive link above it) |
| Outlook.com / Exchange default | 20 MB |
| Many corporate gateways | 10 MB, or lower |
| iCloud Mail | 20 MB |
And a detail that catches people: attachments are base64-encoded in
transit, which inflates them by about a third. A 20 MB file is roughly
27 MB on the wire — over Gmail's cap despite looking under it.
## What is making it big
In descending order of blame:
**Inlined chart libraries, repeatedly.** `plotly.js` is around 3 MB.
Export ten figures with `include_plotlyjs=True` on each and you have
inlined it ten times. Inline once:
```python
parts = [fig.to_html(full_html=False, include_plotlyjs=(i == 0))
for i, fig in enumerate(figs)]
```
**Base64 media.** Screenshots, videos and traces in test reports. In
Playwright, `screenshot: 'only-on-failure'` and `video:
'retain-on-failure'` usually remove most of the payload with no loss to
anyone reading a green run.
**The whole dataset, embedded.** Reports that support client-side
filtering ship the raw rows. Aggregate to what the charts actually plot,
or cap the table and link the full extract.
**Font files, inlined.** Rarely worth their size in a report nobody
prints.
`gzip -9 report.html` will often cut what remains by 80% — but a
recipient who has to un-gzip is a recipient who might not.
## Why zipping is a bad answer
It is the reflex, and it introduces two problems:
1. Corporate mail gateways commonly quarantine or strip archives that
contain HTML, because that combination is a phishing pattern. The
message arrives with the attachment removed and no explanation.
2. The recipient unzips and double-clicks `index.html`, landing on
`file://` — where XHR-loading reports render blank
([Allure](/fix/allure-report-blank-page),
[Playwright](/fix/playwright-report-blank)) and relative asset paths
break ([lost CSS](/html-report-broken-css)).
Email clients also strip `