Hydrogen SEO vs All in One SEO: cost, output and cleanup, measured
Hydrogen SEO is the far lighter plugin: in our benchmark it added +12.9 ms of PHP time and +1 database query per request, against +53.5 ms and +22 for All in One SEO. All in One SEO is the more established, more approachable product, with a guided setup and years of production use that Hydrogen SEO, still in Beta, cannot claim.
We build Hydrogen SEO, so weigh this accordingly. Every figure comes from the seven-plugin benchmark: one WordPress 7.1 install, one plugin active at a time, database restored between runs, each plugin at its own defaults. All in One SEO posted the highest cost in every cost category it entered, and that is the context for this page.
The numbers
| Measured | Hydrogen SEO 0.0.18 | All in One SEO 5.0.1.1 |
|---|---|---|
| Front-end PHP time added | +12.9 ms | +53.5 ms |
| Peak memory added | +4.5 MB | +14.5 MB |
| Database queries added | +1 | +22 |
| Hooks registered | +22 | +100 |
<head> bytes added | +4,259 | +6,668 |
| Meta description by default | Yes | Yes |
| JSON-LD types printed | 10 | 8 |
| Open Graph / X tags | 10 / 5 | 6 / 3 |
| Sitemap URLs listed | 72 | 73 |
| Sitemap image entries | 40 | 0 |
lastmod coverage | 72 / 72 | 73 / 73 |
| Custom database tables | 0 | 9 |
| Autoloaded options added | +0.4 KB | +14.6 KB |
| Plugin package size | 4.6 MB | 24.4 MB |
| Block editor assets | 2 files, 700.4 KB | 130 files, 3,543 KB |
| After deactivation | +0.2 KB left autoloading | No reduction: 14.5 KB still autoloading |
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
The gap between these two is the widest of any pair that includes Hydrogen SEO. On the front end, neither adds a script or stylesheet, so visitors see no difference in asset weight. The difference is on the server: All in One SEO used roughly four times the PHP time, about three times the memory (+14.5 MB against +4.5 MB) and 22 extra queries where Hydrogen SEO used one. It also added 6,668 bytes to <head>, the most in the field, against Hydrogen SEO's 4,259.
The admin tells the same story more loudly. All in One SEO rendered a 511 KB dashboard, about four times bare WordPress, and pulled 130 of its own files (3,543 KB) into the block editor. Hydrogen SEO's dashboard was 131.2 KB against a 129.8 KB baseline, and its editor loads 2 files totalling 700.4 KB. That 700 KB is not small; it is a React bundle, and The SEO Framework and Slim SEO both load far less. But next to All in One SEO it is a fifth of the weight.
Output is closer than cost. Both print a meta description, a canonical and full sitemap lastmod coverage (73 of 73 for All in One SEO, 72 of 72 for Hydrogen SEO). Hydrogen SEO printed 10 JSON-LD types in 2,071 bytes; All in One SEO printed 8 in 4,544, the largest schema payload measured. All in One SEO had the thinnest social output of the major plugins (6 Open Graph, 3 X tags against 10 and 5), and its free sitemap carried no image entries, where Hydrogen SEO's included all 40 featured images.
Cleanup is the last divider. All in One SEO created nine custom tables, more than any other plugin tested, and deactivating it released none of its 14.6 KB of autoloaded options. Hydrogen SEO creates no tables and left 0.2 KB behind. What All in One SEO gives you for all of this is polish: clear screens, sensible defaults, a large product family and a long track record. What Hydrogen SEO adds beyond a lighter build is an AI layer, including an agent you can hand plain-language jobs, which needs a free account.
Choose Hydrogen SEO if
- You want the lower server cost: +12.9 ms and +1 query against +53.5 ms and +22.
- You want no custom database tables and almost nothing left autoloading after deactivation.
- You want featured images in your sitemap and 10 schema types at default settings.
- You want an AI agent that can do bulk jobs like writing missing meta descriptions, and you accept Beta software.
Choose All in One SEO if
- You want a mature, widely used plugin with a guided setup and approachable screens.
- You are already inside its product family and value the integrations.
- Your hosting has headroom and the extra queries and 511 KB dashboard do not bother you.
Switching between them
Hydrogen SEO's Tools → Import SEO Data detects All in One SEO and All in One SEO Pro and brings across title and description templates, robots rules, social defaults, per-post SEO fields and Pro redirect rules, with a dry run first and an Undo afterwards. One detail matters here: All in One SEO keeps per-post data in its own tables, so run the import before you uninstall it, since uninstalling can remove those tables. Deactivating is fine. The full list of what moves and what does not is in switch from another SEO plugin. Going the other way, All in One SEO has its own importer for several major plugins; check its documentation for current sources.
Common questions
Is Hydrogen SEO faster than All in One SEO?
On our benchmark rig, yes. Hydrogen SEO 0.0.18 added +12.9 ms of PHP time and +1 query; All in One SEO 5.0.1.1 added +53.5 ms and +22 queries. Timings are relative costs on one machine, not predictions for your host.
Does All in One SEO leave data behind after deactivation?
In our test, deactivating it did not reduce its autoloaded options at all: 14.5 KB kept loading on every request, and its nine custom tables remained. Hydrogen SEO left 0.2 KB and creates no tables.
Which prints better schema?
Hydrogen SEO printed 10 JSON-LD types in 2,071 bytes; All in One SEO printed 8 types in 4,544 bytes. Both were valid at defaults. More types is not automatically better, but Hydrogen SEO covered more of the page in fewer bytes.
Can I move from All in One SEO to Hydrogen SEO without losing work?
Yes. The built-in importer previews every change, imports settings, per-post fields and Pro redirects, and keeps an Undo. Run it before uninstalling All in One SEO, because its per-post data lives in its own tables.