# marcelduran/yslow

YSlow analyzes web pages and suggests ways to improve their performance based on a set of rules for high performance web pages.

Repository: https://github.com/marcelduran/yslow
Canonical: https://ross.abutalabs.com/products/yslow
Language: JavaScript
License: BSD-3-Clause
License Family: permissive
Last push: 2023-02-17T15:15:27+00:00

## Health v2 (maintenance only)
Score: 32/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 0, release rhythm 35, longevity 100
- inputs: {"age_days": 5334, "days_push": 1293, "days_rel": null, "gap_med": null, "n_releases_24m": 0}
- flags: no_releases
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 2200, forks 373 (observed 2026-08-28T04:06:25.565308+00:00)

## What it is
YSlow analyzes web pages and grades their performance against Yahoo's rules for high performance web pages. It ships as browser extensions, a bookmarklet, and a Node.js/PhantomJS command-line tool that analyzes HAR files.

## Use cases
- analyze web page performance against best-practice rules
- audit page load speed from HAR files on the command line
- find why my website loads slowly
- grade web pages for performance optimizations
- run headless web performance analysis in CI
- measure front-end performance of a web page

## When to choose
- you want classic Yahoo performance-rule grading of web pages
- you need a CLI to analyze HAR files for performance issues
- you want a browser extension or bookmarklet for on-page performance audits

## When to avoid
- you need modern Core Web Vitals metrics like LCP or CLS
- you want actively developed tooling - the project is largely in maintenance mode
- you need full Lighthouse-style audits including accessibility and SEO

## Facets
- artifact type: cli-tool
- maturity: maintenance
- function: analytics, monitoring, http-client, browser-extension
- domain: web-development, performance, developer-tools, frontend
- platform: browser, cli, cross-platform
- tags: web-performance, page-speed, har-analysis, yahoo-rules, phantomjs, bookmarklet, nodejs

## Member repositories
- marcelduran/yslow (main) score 32

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:06:25.565308+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-30T02:47:05.719550+00:00, confidence not recorded.
  - readme: https://github.com/marcelduran/yslow (fetched 2026-08-28T04:06:25.565308+00:00, sha eca20ce84fd9)
- Data as of 2026-08-30T08:39:29.467469+00:00.