Smart format routing
The web-perf preset converts JPEG to WebP and routes each PNG to WebP (opaque) or AVIF (transparent). One config line, the right decision per file.
Open source · MIT · v1.0.0
Optimize your static assets.Locally.
A Node.js CLI for images, CSS, JS, and SVG. Smart format routing, incremental cache, one command. No upload, no account, no SaaS.
$ npm install -g @assetopt/cli
~/my-project
$ assetopt optimize ./public
Loading config from .assetoptrc … preset: web-perf
Found 47 assets (images, css, js, svg)
✓ hero.jpg 4.2 MB → 1.7 MB -59.5%
✓ portrait.png 3.8 MB → 540 KB -86.1% (smart-routed → webp)
✓ logo.png 1.4 MB → 260 KB -81.9% (smart-routed → avif)
✓ styles.css 3.3 KB → 1.5 KB -54.0%
✓ app.js 2.8 KB → 810 B -71.7%
Total: 12.4 MB → 2.9 MB (-77%) — in 3.8sWhy assetopt
Built for real folders, not benchmark demos.
Four things assetopt does that one-off compression tools don't.
Incremental cache
A sha256 manifest tracks every source and its config. Re-running optimize skips unchanged files. First run is slow, every run after is near-instant.
Multi-asset, one command
Images, CSS, JS, and SVG in the same pass — sharp, lightningcss, esbuild, svgo wired together so you don't glue four tools yourself.
Local. Free. MIT.
No upload, no account, no SaaS, no telemetry. Your assets stay on your machine. The CLI is MIT and feature-complete on its own.
Quickstart
Three commands. No config dance.
From zero to optimized assets in under a minute. Already have a build pipeline? Drop the optimize step into your CI and skip step 1.
- 1
Initialize
Generate a default .assetoptrc at the root of your project.
$ assetopt init - 2
Analyze
Dry-run: see potential savings without writing anything to disk.
$ assetopt analyze ./public - 3
Optimize
Write optimized assets to ./optimized/. Originals are untouched.
$ assetopt optimize ./public
Cached on re-runFull reference in thedocs.
What you get
Real files. Real numbers.
Every figure below comes from running assetopt on the downloadable sample pack with the
web-perf
preset. Drag each slider — same pixels, far fewer bytes. The
smart routing layer splits PNGs by transparency.
Original · 5.2 MBassetopt · WEBP · 539 KB
PNG · opaquesmart-routed
PNG export (opaque)
−89.8%Original5.2 MB
assetopt → WEBP539 KB
An opaque PNG — smart-routed to WebP, which beats AVIF on this content.
Photo via Lorem Picsum / Unsplash
Original · 56 KBassetopt · AVIF · 9 KB
PNG · transparentsmart-routed
PNG logo (transparent)
−83.3%Original56 KB
assetopt → AVIF9 KB
A logo PNG with alpha — smart-routed to AVIF, which keeps transparency at a far smaller size.
Designed for this pack · CC0
Original · 1.7 MBassetopt · WEBP · 1.4 MB
JPEG
JPEG photo
−17.4%Original1.7 MB
assetopt → WEBP1.4 MB
A heavy photo export. The web-perf preset converts it to WebP at matched quality.
Photo via Lorem Picsum / Unsplash
CSSmain.css
2 KB → 1 KB
JSapp.js
2 KB → 984 B
SVGdiagram.svg
2 KB → 1 KB
Whole pack : 7.9 MB → 2.7 MB. Your gains depend on how compressed your sources already are.
−65.3% totalTry it yourself
Don't trust the numbers. Reproduce them.
Download the exact pack these figures come from. It ships with the
.assetoptrc
used above — run two commands and you'll land on the same
−65.3%. Nothing is uploaded; everything runs on your machine.
Sample asset pack
Photos, PNGs, an SVG, CSS and JS — plus the config. 7.8 MB zip.
- 1
Unzip and step in
$ unzip sample-assets.zip -d sample-assets && cd sample-assets - 2
See the savings (writes nothing)
$ npx @assetopt/cli analyze . - 3
Optimize for real (→ ./optimized)
$ npx @assetopt/cli optimize .
No global install needed — npx fetches the CLI on first run. Your originals are never touched; results land in ./optimized.
Workflows
Three ways to fit it in your pipeline.
Pick the one that matches your project — each has its own guide and its own safe-default configuration.
01
CI pre-deploy
You have a build (Vite, Next, Astro…) producing a dist/ folder. Optimize the bundle as a CI step before deploy.
Best for · Most projects with a frontend framework.
Safe with web-perf preset
Read the guide
02
Hand-written static site
You write HTML by hand and reference images by their literal filenames.
Best for · Personal sites, simple landing pages.
Use formatMatrix: keep
Use formatMatrix: "keep" — the web-perf preset would rewrite extensions and break your <img> tags.
Read the guide
03
Asset prep before integration
You receive raw assets from a designer or client, optimize them, then write the markup yourself.
Best for · Working with designers, client deliverables.
Safe with web-perf preset
Read the guide
FAQ
Questions before you install.
Three of the most common ones below. The full FAQ covers integration edge cases.
Is it safe to enable the web-perf preset in production?
Yes, in two of the three supported workflows. If a bundler wraps your assets (Vite, Next, Astro…), it rewrites references safely — go ahead. Same for asset prep when you write the HTML yourself afterward. The one case to avoid is hand-written static sites where images are referenced by literal filename — there, set formatMatrix to "keep" per format so extensions are preserved.
How is this different from TinyPNG, imagemin, or Squoosh?
Three things. It runs locally with no upload or account — your assets stay on your machine. It handles four asset types in one command (images, CSS, JS, SVG), so you don't glue four tools yourself. And the incremental cache means re-runs only process changed files, which makes it practical to put inside CI.
Will the incremental cache actually save time in CI?
On a typical re-deploy where you touched two or three assets, the cache skips the rest — runs drop from minutes to seconds. The manifest hashes source bytes, resolved config, and the @assetopt/core version, so it self-invalidates when anything that matters changes. Persist the .assetopt-cache.json file across CI runs and it keeps paying off.