# Share a BackstopJS Report — Visual Diffs Someone Can Actually Approve

Canonical: https://commareports.com/share-backstopjs-report
Published: 2026-09-01

> BackstopJS writes an HTML report with reference, test and diff images side by side. Publish it to Comma so the approve-or-fix decision happens on the diff itself, with a revision per run.

# Share a BackstopJS report

Visual regression testing has a well-known failure mode, and it is not
technical. The suite runs, produces forty diffs, and then waits for a
human to say which ones are intended. That human is usually a designer,
and the report is usually on a CI worker behind a login they do not have.

So the diffs get screenshotted into Slack, one at a time, and the
approval conversation happens next to a cropped image with an arrow
drawn on it.

## Publish it

```bash
npx backstop test || true

curl -fsS -X PATCH \
  "https://commareports.com/api/v1/reports/$COMMA_REPORT_ID" \
  -H "Authorization: Bearer $COMMA_API_TOKEN" \
  -H "Content-Type: application/json" \
  -d "$(jq -n --rawfile html backstop_data/html_report/index.html \
        --arg title "Visual diffs — $BRANCH — build $BUILD_NUMBER" \
        '{title: $title, html: $html}')"
```

The report is image-heavy by nature, so dragging
`backstop_data/html_report/` into [the app](https://commareports.com/) is
usually the better route: the reference, test and diff images upload as
assets and their references are rewritten to the uploaded copies. Publish
the index alone and you get a report shaped like a visual diff with no
visuals in it.

`|| true` because `backstop test` exits non-zero whenever anything
differs, which is every run you care about.

## What the URL changes

- **Approval happens on the diff.** "Intended — new spacing scale" or
  "regression, DES-77" pinned to the scenario. See
  [commenting on HTML](/comment-on-html).
- **The designer needs no tooling.** A link, in a browser, on a phone.
- **Run-over-run history.** Same URL, revision per run, so the
  conversation about last week's diff is still there.
- **Private by default** — pre-release UI is not something to leave on a
  guessable URL. See the [sharing model](/docs/sharing).

## Limits

- **Entry HTML: 5 MB.** Assets: 25 MB per file, **250 MB and 500 files
  total** — three images per scenario per viewport adds up quickly.
  Publish per section when the matrix is large.
- **Scripts run, sandboxed**: `allow-scripts`, no `allow-same-origin`.
- **60 requests/minute per token.**

## Try it

Comma is free — unlimited reports, unlimited commenters, unlimited
revision history.

**[Create your first report →](https://commareports.com/)**

### Related

- [Storybook static builds](/share-storybook-static) — the components themselves
- [Accessibility reports](/share-accessibility-report) · [Lighthouse](/share-lighthouse-report)
- [Share with a client](/share-html-file-with-client) · [Publish from CI](/docs/ci)