Yoast SEO vs Slim SEO: full-featured against near-invisible
Slim SEO costs about a quarter of what Yoast SEO does on the server, +10.0 ms against +39.0 ms, and its output is closer to Yoast's than the size gap suggests: 10 schema types against 12, and 73 sitemap URLs with images against 75. Yoast is ahead on sitemap lastmod, X tags and, above all, configuration and ecosystem.
Figures are from our seven-plugin benchmark, free versions at defaults, one plugin active at a time on WordPress 7.1. We build Hydrogen SEO, which is not in this pair.
The numbers
| Measured | Yoast SEO 28.4 | Slim SEO 4.10.1 |
|---|---|---|
| Front-end PHP time added | +39 ms | +10 ms |
| Peak memory added | +10.5 MB | +2 MB |
| Database queries added | +3 | +2 |
| Hooks registered | +187 | +51 |
<head> bytes added | +5,656 | +1,649 |
| Meta description by default | No | Yes |
| JSON-LD types printed | 12 | 10 |
| Open Graph / X tags | 10 / 5 | 11 / 2 |
| Sitemap URLs listed | 75 | 73 |
| Sitemap image entries | 40 | 40 |
lastmod coverage | 74 / 75 | 50 / 73 |
| Custom database tables | 6 | 0 |
| Autoloaded options added | +13.6 KB | -0.2 KB |
| Plugin package size | 21 MB | 1.4 MB |
| Block editor assets | 48 files, 4,160 KB | 14 files, 187.7 KB |
| After deactivation | +2.6 KB left autoloading, 6 tables remain | Releases everything |
Measured on one WordPress 7.1 install (PHP 8.2, MySQL 8.0, Twenty Twenty-Five, 40 posts), each plugin alone with default settings, against a no-plugin baseline. Bold marks the better number in each row. Full method: how we tested.
What the numbers mean
Slim SEO is one of the two lightest plugins we measured. It added +2.0 MB of memory against Yoast's +10.5 MB, 51 hooks against 187, grew <head> by just 1,649 bytes against 5,656, and ships 1.4 MB, the smallest package in the test, against Yoast's 21.0 MB. Its autoloaded options came out fractionally below baseline, where Yoast added 13.6 KB. It creates no tables; Yoast creates six. Queries were close (2 against 3).
Output is where this pair surprises. Slim SEO printed 10 JSON-LD types in 3,828 bytes, almost the same payload as Yoast's 12 types in 3,976. Both sitemaps include taxonomy archives and all 40 featured images (73 URLs for Slim SEO, 75 for Yoast). The difference is freshness data: Yoast stamped lastmod on 74 of 75 URLs, Slim SEO on 50 of 73. Slim SEO printed a meta description by default and Yoast did not. On social tags Slim SEO printed 11 Open Graph tags but only 2 X tags, against Yoast's 10 and 5.
The admin is the other big split. Slim SEO adds no admin menu items at all and loads 187.7 KB into the editor. Yoast adds two menus and 4,160 KB, the heaviest editor we measured. That is a philosophy, not an accident: Slim SEO is built to be set once and forgotten, with very little to configure. Yoast gives you settings, content analysis and a large ecosystem to work with.
On deactivation Slim SEO released everything; Yoast left 2.6 KB of autoloaded options and its six tables.
Choose Yoast SEO if
- You want full
lastmodcoverage in your sitemap. - You want more X card tags and more schema types.
- You want settings to control, plus content analysis and a large ecosystem.
- You are willing to pay in server and editor weight for that.
Choose Slim SEO if
- You want a tiny footprint: 1.4 MB package, +1,649 head bytes, no tables.
- You want nearly Yoast-sized schema and a sitemap with images at a quarter of the cost.
- You want a plugin with no admin menus and nothing to maintain.
- You do not rely on X card output.
Switching between them
Slim SEO includes a migration tool that can import Yoast data; check its documentation for exactly what moves. Because Slim SEO has so few settings, most of what matters is per-post titles, descriptions and redirects, so verify those on a sample of pages after the move. Going from Slim SEO to Yoast has less vendor tooling, and Yoast's settings will need configuring from scratch. Hydrogen SEO imports from both; see switch from another SEO plugin.
Common questions
Is Slim SEO lighter than Yoast?
Yes: +10.0 ms, +2.0 MB and a 1.4 MB package against Yoast's +39.0 ms, +10.5 MB and 21.0 MB. Slim SEO creates no tables; Yoast creates six.
Does Slim SEO print as much schema as Yoast?
Nearly. Slim SEO printed 10 JSON-LD types in 3,828 bytes; Yoast printed 12 in 3,976 bytes.
What is Slim SEO's weak spot?
Sitemap freshness and X tags. It left 23 of 73 sitemap URLs without lastmod and printed only 2 X tags, against Yoast's 74 of 75 and 5 tags.