# Share a Criterion.rs Benchmark Report — Plots and All

Canonical: https://commareports.com/share-criterion-benchmark-report
Published: 2026-09-08

> cargo bench writes target/criterion/report — a folder of linked pages and SVG plots that breaks when opened from the filesystem. Publish it to Comma for a working URL.

# Share a Criterion.rs benchmark report

Criterion does the statistics most benchmarking skips. It estimates the mean
*and* the distribution, compares against a stored baseline, and tells you
whether the change it measured is outside the noise — with plots that make an
outlier obvious rather than something you have to infer from a single number.

```bash
cargo bench                       # → target/criterion/report/index.html
```

And then the report is a directory:

```
target/criterion/
├─ report/index.html          ← the entry point
├─ parse_json/
│  ├─ report/index.html       ← per-benchmark page
│  ├─ pdf.svg  violin.svg  regression.svg
│  └─ change/                 ← comparison against the previous baseline
└─ serialize/…
```

Sending `index.html` on its own gives the reader a page of dead links. Zipping
it gives them a chore. Screenshotting the violin plot throws away the reason
Criterion drew a violin plot.

## Publish the folder

Drag `target/criterion/report/` — or the whole `target/criterion/` if you want
the per-benchmark drilldowns — into [the app](https://commareports.com/):

- `index.html` becomes the **report body**.
- The per-benchmark pages and every generated SVG upload alongside it, and
  their relative references are rewritten to the uploaded copies, so clicking
  through to a specific benchmark works.
- Scripts and inline SVG render inside a sandboxed iframe (`allow-scripts`, no
  `allow-same-origin`).

Or PATCH the entry file from a script:

```bash
cargo bench

curl -fsS -X PATCH "https://commareports.com/api/v1/reports/$REPORT_ID" \
  -H "Authorization: Bearer $COMMA_API_TOKEN" \
  -H "Content-Type: application/json" \
  -d "$(jq -n --rawfile html target/criterion/report/index.html \
        --arg t "Criterion — parser, $(git rev-parse --short HEAD)" \
        '{title: $t, html: $html}')"
```

## Publish the comparison, not just the run

The most valuable page Criterion generates is `change/` — the comparison
against the saved baseline, with the verdict and its confidence interval. Save
a named baseline before a change and compare against it after:

```bash
git checkout main
cargo bench -- --save-baseline main

git checkout my-optimization
cargo bench -- --baseline main
```

The generated report now contains "Performance has improved" (or has not) with
the interval attached. That is the artifact worth a URL in the pull request,
because it is the one a reviewer can disagree with on the evidence.

## From CI

Runner noise makes absolute numbers unreliable, but Criterion's own noise
modelling means the *verdict* holds up better than a raw comparison would. PATCH
one report id per suite and set a wide regression threshold:

```bash
cargo bench -- --baseline main --noise-threshold 0.05
```

One URL, a revision per run, and the revision list makes the runner's variance
visible instead of leaving you to guess at it.

## What review adds

- **Anchored threads** on the benchmark under discussion — see
  [commenting on HTML](/comment-on-html).
- **Revisions**, so a claimed speedup is checkable later.
- **Access per report** — private, team, domain-gated or named reviewers. See
  the [sharing model](/docs/sharing).

## Limits

- **Entry HTML: 5 MB.** Assets: 25 MB per file, 250 MB and 500 files total.
  Criterion generates several SVGs per benchmark, so a suite with hundreds of
  benchmarks is the case that approaches the 500-file cap — publish
  `report/` alone rather than all of `target/criterion/` when it does.
- **60 requests/minute per token.**

## Try it

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

**[Publish a benchmark →](https://commareports.com/)**

### Related

- [Share a JMH benchmark report](/share-jmh-benchmark-report) · [Share a benchmark report](/share-benchmark-report)
- [Share a Rust coverage report](/share-rust-coverage-report) · [Share rustdoc](/share-rustdoc)
- [Share a flame graph](/share-flamegraph) · [Share an HTML folder](/share-html-folder)