Verdict: Slim SEO is the lightest SEO plugin we measured, and its free version includes redirects. It added 23 ms to each visitor page in Accelera’s test, a third of Yoast’s 71 ms. The catch: the free version gives no keyword or writing advice.
Key takeaways
- It added 23 ms to each visitor page, against 69 ms for Rank Math and 71 ms for Yoast (Accelera).
- The free plugin is 1.5 MB and 225 files, and it includes redirects and a 404 log.
- No keyword or writing advice for free. Pro costs $59 a year for 1 site and renews at the same price.
This review uses public data only: WordPress.org, the plugin’s code, its pricing page, an independent speed test and our own scan of the top 10,000 sites. For the record, this site runs Rank Math, and we have no affiliate deal with any SEO plugin.
Slim SEO at a glance
| Made by | eLightUp (Anh Tran), the team behind Meta Box |
| On WordPress.org since | December 2018 |
| Active installs | 70,000+ |
| Rating | 4.7 from 136 reviews (3.7% one-star) |
| Current version | 4.11.0, released 28 September 2026 |
| Releases in the last 12 months | 23 |
| Tested up to | WordPress 7.1.2 (the current version) |
| Installed size | 1.5 MB, 225 files |
| Pro plans | $59 to $179 a year (1 site to unlimited) |
What you get for free
The free plugin sets up the basics on its own: the readme says it “doesn’t have any settings page”, though there is one for the options. In the code of version 4.11.0 we found:
- automatic titles and meta descriptions, which you can override on each post, page and category
- an XML sitemap with image and Google News entries, canonical URLs, and Open Graph, Twitter and LinkedIn tags
- schema for the site, each page, articles, breadcrumbs, the organization and the author, plus a breadcrumb shortcode and block
- a redirect manager, automatic redirects when you change a slug, and an optional 404 log
- AI titles and descriptions, one by one or in bulk, with your own OpenAI, Gemini, Claude or OpenRouter API key
- a robots.txt editor, header and footer code, and an option to remove the category base from URLs
The one upgrade prompt is an “Upgrade” link next to the plugin in your plugins list. We found no banners or upsell boxes in the code. Its only admin notices warn about real problems, such as a site hidden from search engines.
What is missing from the free plugin: there are no focus keywords, no content score and no readability check. There is no llms.txt and no IndexNow either. The AI feature is free, but your AI provider bills you for each request.
What Pro costs
Slim SEO Pro starts at $59 a year for 1 site, and the pricing page says it renews at the same price. Every plan has all the Pro features.
| Plan | Sites | Price a year |
|---|---|---|
| Free | Unlimited | $0 |
| Personal | 1 | $59 |
| Freelancer | 10 | $119 |
| Agency | Unlimited | $179 |
Pro adds a visual schema builder with 30+ schema types, internal link suggestions, a broken link monitor and Search Console reports. It also adds a writing assistant with tips on keywords, images, links and readability. Rank Math and Yoast give that kind of guidance away for free.
For comparison, SEOPress PRO costs $49 a year for 1 site. The SEO Framework charges $84 a year for 2 sites. AIOSEO renews at $99 a year for 1 site, and Yoast SEO Premium costs €118.80 a year per site.
Speed: the fastest of six
Slim SEO was the fastest of the six SEO plugins Accelera timed on a clean WordPress install (full test, with Slim SEO 3.25.3, updated September 2026):
| Plugin | Visitor page | Admin | Editor |
|---|---|---|---|
| Slim SEO | 23 ms | 13 ms | 20 ms |
| Rank Math | 69 ms | 73 ms | 96 ms |
| Yoast SEO | 71 ms | 95 ms | 177 ms |
In the post editor, Slim SEO loads 16 KB of JavaScript, against 190 KB for Rank Math and 678 KB for Yoast. Accelera tested an older version. Version 4.11.0 has added AI and other features since, so treat 23 ms as a guide, not a promise. On fast hosting you won’t feel the difference. On cheap shared hosting, with other plugins, it adds up.
It is also the smallest on disk. We unzipped the current free version of each plugin on 6 October 2026.
Updates and support
Slim SEO ships often. Its changelog lists 23 releases between October 2025 and October 2026, and the latest, 4.11.0, came out on 28 September 2026. It is tested up to WordPress 7.1.2, the current version.
Two of those releases fixed security issues: an AI endpoint that disclosed content (4.9.9, June 2026) and a post data leak in preview routes (4.9.11, July 2026). Both were patched, and the plugin reports bugs through Patchstack. Update it like any other plugin.
Version 4.11.0 also connects Slim SEO to the WordPress Abilities API. AI agents with access to your site can read and update its titles and descriptions. How that connection works: WordPress MCP.
Who uses it?
On 29 September 2026 we scanned the homepages of the top 10,000 sites in the Tranco ranking. Of 716 WordPress sites, 323 showed Yoast, 74 Rank Math and 1 Slim SEO: Heroku. We re-checked it by hand on 6 October 2026. Heroku runs Yoast SEO Premium for its tags and Slim SEO for its schema.
Slim SEO is hard to spot. It prints no comment in the page code, so we detect it through its schema tag. Sites that turn schema off won’t show up in our count. You can check any site with our plugin detector.
Switching to and from Slim SEO
- From Yoast, Rank Math, SEOPress, AIOSEO, The SEO Framework or Squirrly: the built-in migration tool copies titles, descriptions, social images and noindex settings.
- Redirects: it imports them from Rank Math, SEOPress, Yoast Premium, Redirection and 301 Redirects. Focus keywords are not moved.
- To SEOPress: SEOPress 10.3 has an importer for Slim SEO. It copies titles, descriptions, social images and noindex.
- To Yoast, Rank Math, AIOSEO or The SEO Framework: we found no importer for Slim SEO in Yoast 28.6, Rank Math 1.0.279, AIOSEO 5.0.2.1 or The SEO Framework 5.1.4.
Pros and cons
- Pro: fastest of six in Accelera’s test, at a third of Yoast’s time
- Pro: 1.5 MB installed, with one upgrade link and no banners
- Pro: free redirects, 404 log and AI titles
- Pro: 23 releases in a year, tested with the current WordPress
- Con: no keyword or writing advice unless you pay for Pro
- Con: 70,000 installs, far fewer than Yoast or Rank Math
- Con: only SEOPress can import its data
Should you use Slim SEO?
- Yes, if speed comes first and you know what a good title looks like.
- Yes, if you want redirects without a second plugin. The SEO Framework, the other light option, has only a redirect field on each page.
- No, if you want keyword guidance for free. Rank Math and Yoast both include it.
- No, if you want the safest exit. Most plugins can’t import its data. See the best SEO plugins for WordPress.
What to do next
- Try it on a staging site first, and turn off your old SEO plugin only after the migration.
- Coming from Yoast, Rank Math, SEOPress or AIOSEO: back up, run Slim SEO’s migration tool, then check 5 pages and your redirects.
- Want AI titles: add your own API key, and check your provider’s price before a bulk run.
- Want keyword tips: pick Pro, or stay with Rank Math or Yoast.
See what a competitor runs
Paste any address into our free plugin detector to see its SEO plugin, theme and every plugin that loads on the page.
FAQ
Is Slim SEO free?
Yes. The free plugin covers titles, descriptions, sitemaps, schema, breadcrumbs, redirects, a 404 log and AI titles with your own API key. Slim SEO Pro costs $59 a year for 1 site, $119 for 10 and $179 for unlimited sites.
Is Slim SEO better than Yoast?
On speed, yes: it added 23 ms to each visitor page against 71 ms for Yoast in Accelera’s test, and it is 1.5 MB installed against 21 MB. Yoast is better if you want focus keywords and readability advice for free.
Is Slim SEO faster than The SEO Framework?
Yes, in Accelera’s test: 23 ms per visitor page against 35 ms. The SEO Framework was faster in the admin dashboard, 6 ms against 13 ms. Both took 20 ms in the post editor.
Does Slim SEO have redirects?
Yes, in the free version. It has a redirect manager, automatic redirects when you change a post’s slug and an optional 404 log. It can import redirects from Rank Math, SEOPress, Yoast Premium, Redirection and 301 Redirects.
Does Slim SEO have focus keywords?
Not in the free plugin. It has no focus keyword field, content score or readability check. Slim SEO Pro adds a writing assistant with tips on keywords, images, links and readability.