YSlow Ruleset Matrix
YSlow analyzes web pages and why they're slow based on Yahoo!'s rules for high performance web sites
Matrix Table Keys
- Rule: The YSlow performance rule
- Weight: How this performance rule is weighted in the overall page analyis grade
- Points: Number of points deducted per offender (performance infraction occurance), from a total of 100 per rule
- Configs: How many points/threshold per component will be used for computation
- Score Computation: The formula used to compute the final score per rule
- Grades from A to F: How many components/offenders is necessary to reach grades from A to F
| Rule | Weight | Points | Configs | Score Computation | (A) 90 <= S <= 100 |
(B) 80 <= S < 90 |
(C) 70 <= S < 80 |
(D) 60 <= S < 70 |
(E) 50 <= S < 60 |
(F) 0 <= S < 50 |
| Make fewer HTTP requests | 8 | js = 3 css = 4 css images = 3 |
max js = 3 max css = 2 max css images = 6 |
(N JS - 3) * 3 (N CSS - 2) * 4 (N CSS images - 6) * 3 |
0 to 6 JS OR 0 to 4 CSS OR 0 to 9 CSS images |
7 to 9 JS OR 5 to 7 CSS OR 10 to 12 CSS images |
10 to 13 JS OR 8 to 9 CSS OR 13 to 16 CSS images |
14 to 16 JS OR 10 to 12 CSS OR 17 to 19 CSS images |
17 to 19 JS OR 13 to 14 CSS OR 20 to 22 CSS images |
>= 20 JS OR >= 15 CSS OR >= 23 CSS images |
| Use a CDN | 6 | 10 | patterns = CDN hostname RegExp patterns types = js, css, image, cssimage, flash, favicon |
N RegExp mismatches * 10 (ignores /favicon.ico) |
0 or 1 of any type | 2 of any type | 3 of any type | 4 of any type | 5 of any type | >= 6 of any type |
| Avoid empty src or href | 30 | 100 | - | N empty src <img> * 100 N empty src <script> * 100 N empty href <link rel="stylesheet"> * 100 |
0 empty src <img> AND 0 empty src <script> AND 0 empty href <link rel="stylesheet"> |
- | - | - | - | >= 1 empty src <img> OR >= 1 empty src <script> OR >= 1 empty href <link rel="stylesheet"> |
| Add Expires headers | 10 | 11 | how far = 172800s (2 days) types = js, css, image, cssimage, flash, favicon |
N (unexpired or expiring in < 2 days of any type) * 11 | 0 unexpired or expiring in < 2 days of any type | 1 unexpired or expiring in < 2 days of any type | 2 unexpired or expiring in < 2 days of any type | 3 unexpired or expiring in < 2 days of any type | 4 unexpired or expiring in < 2 days of any type | >= 5 unexpired or expiring in < 2 days of any type |
| Compress components with GZip | 8 | 11 | min file size = 500 bytes types = doc, iframe, xhr, js, css |
N (uncompressed or file size < 500b of any type) * 11 | 0 uncompressed or file size < 500b of any type | 1 uncompressed or file size < 500b of any type | 2 uncompressed or file size < 500b of any type | 3 uncompressed or file size < 500b of any type | 4 uncompressed or file size < 500b of any type | >= 5 uncompressed or file size < 500b of any type |
| Put CSS at top | 4 | 10 | - | 1 + N CSS link tag on BODY * 10 | 0 CSS link tag on BODY | 1 CSS link tag on BODY | 2 CSS link tag on BODY | 3 CSS link tag on BODY | 4 CSS link tag on BODY | >= 5 CSS link tag on BODY |
| Put JavaScript at bottom | 4 | 5 | - | N JS on HEAD * 5 ignores injected, defered and async JS |
0 to 2 JS on HEAD | 3 or 4 JS on HEAD | 5 or 6 JS on HEAD | 7 or 8 JS on HEAD | 9 or 10 JS on HEAD | >= 11 JS on HEAD |
| Avoid CSS expressions | 3 | 2 | - | N expressions on CSS links or inline STYLE * 2 | 0 to 5 expressions on CSS or inline STYLE | 6 to 10 expressions on CSS or inline STYLE | 11 to 15 expressions on CSS or inline STYLE | 16 to 20 expressions on CSS or inline STYLE | 21 to 25 expressions on CSS or inline STYLE | >= 26 expressions on CSS or inline STYLE |
| Make JavaScript and CSS external | 4 | n/a | - | none | - | - | - | - | - | - |
| Reduce DNS lookups | 3 | 5 | max domains = 4 | N domains > 4 AND (N domains - 4) * 5 |
0 to 6 domains | 7 or 8 domains | 9 or 10 domains | 11 or 12 domains | 13 or 14 domains | >= 15 domains |
| Minify JavaScript and CSS | 4 | 10 | types = js, css | N (unminified JS or CSS external or inline) * 10 | 0 or 1 unminified component | 2 unminified components | 3 unminified components | 4 unminified components | 5 unminified components | >= 6 unminified components |
| Avoid URL redirects | 4 | 10 | - | N redirects * 10 | 0 or 1 redirect | 2 redirects | 3 redirects | 4 redirects | 5 redirects | >= 6 redirects |
| Remove duplicate JavaScript and CSS | 4 | 5 | types = js, css | N (duplicated JS or CSS) * 5 | 0 to 2 duplicated JS or CSS | 3 or 4 duplicated JS or CSS | 5 or 6 duplicated JS or CSS | 7 or 8 duplicated JS or CSS | 9 or 10 duplicated JS or CSS | >= 11 duplicated JS or CSS |
| Configure ETags | 2 | 11 | types = js, css, image, cssimage, flash, favicon | N bad etag of any type * 11 | 0 bad etag of any type | 1 bad etag of any type | 2 bad etags of any type | 3 bad etags of any type | 4 bad etags of any type | >= 5 bad etags of any type |
| Make AJAX cacheable | 4 | 5 | min cache time = 3600s | N (uncached or expiring in < 3600s) XHR * 5 | 0 to 2 uncacheable XHR | 3 or 4 uncacheable XHR | 5 or 6 uncacheable XHR | 7 or 8 uncacheable XHR | 9 or 10 uncacheable XHR | >= 11 uncacheable XHR |
| Use GET for AJAX requests | 3 | 5 | - | N XHRs not using GET * 5 | 0 to 2 XHRs not using GET | 3 or 4 XHRs not using GET | 5 or 6 XHRs not using GET | 7 or 8 XHRs not using GET | 9 or 10 XHRs not using GET | >= 11 XHRs not using GET |
| Reduce the number of DOM elements | 3 | 10 | range = 250 max dom = 900 |
N DOM elements > 900 AND (N DOM elements - 900) / 250 * 10 |
0 to 1150 DOM elements | 1151 to 1400 DOM elements | 1401 to 1650 DOM elements | 1651 to 1900 DOM elements | 1901 to 2150 DOM elements | >= 2151 DOM elements |
| Avoid HTTP 404 (Not Found) error | 4 | 5 | types = js, css, image, cssimage, flash, favicon, xhr | N 404 * 5 | 0 to 2 404 | 3 or 4 404 | 5 or 6 404 | 7 or 8 404 | 9 or 10 404 | >= 11 404 |
| Reduce cookie size | 3 | 10 | max cookie size = 1000 | cookie size > 1000 AND 1 + (cookie size / 1000) * 10 |
0 to 1000 bytes cookies | 1001 to 1900 bytes cookies | 1901 to 2900 bytes cookies | 2901 to 3900 bytes cookies | 3901 to 4900 bytes cookies | >= 4901 bytes cookies |
| Use cookie-free domains | 3 | 5 | types = js, css, image, cssimage, flash, favicon | N (components of any type with cookies of any size) * 5 ignores /favicon.ico |
0 to 2 components with cookie | 3 or 4 components with cookie | 5 or 6 components with cookie | 7 or 8 components with cookie | 9 or 10 components with cookie | >= 11 components with cookie |
| Avoid AlphaImageLoader filter | 4 | 5 | half points = 2 | N alpha filters * 5 + M _hack alpha filters * 2 | 0 to 2 alpha filters OR 0 to 5 _hack alpha filters |
3 or 4 alpha filters OR 6 to 10 _hack alpha filters |
5 or 6 alpha filters OR 11 to 15 _hack alpha filters |
7 or 8 alpha filters OR 16 to 20 _hack alpha filters |
9 or 10 alpha filters OR 21 to 25 _hack alpha filters |
>= 11 alpha filters OR >= 26 _hack alpha filters |
| Do not scale images in HTML | 3 | 5 | - | N (images scaled down width or height) * 5 | 0 to 2 scaled down images | 3 or 4 scaled down images | 5 or 6 scaled down images | 7 or 8 scaled down images | 9 or 10 scaled down images | >= 11 scaled down images |
| Make favicon small and cacheable | 2 | 5 | size = 2000b min cache time = 3600s |
Favicon 404 not found = 5 Favicon size > 2000b = 5 No favicon expiration or expiration < 3600s = 5 |
Favicon is found AND Any favicon size Any expiration or not OR Favicon is not found AND Any expiration or not (usually not) |
- | - | - | - | - |