Hydrogen SEO vs SEOPress: schema, sitemaps and weight, measured
The deciding difference is structured data. At default settings SEOPress free printed no JSON-LD at all on a standard post, while Hydrogen SEO printed 10 schema types in 2,071 bytes. On cost the two are closer than most pairs: both added one database query, and SEOPress kept its editor lighter, though Hydrogen SEO used about half the PHP time.
We build Hydrogen SEO, and SEOPress is a plugin we respect: in our benchmark it was the cheapest of the long-established feature-rich plugins and it keeps its admin restrained. Here is where each one is ahead.
The numbers
| Measured | Hydrogen SEO 0.0.18 | SEOPress 10.2 |
|---|---|---|
| Front-end PHP time added | +12.9 ms | +24.5 ms |
| Peak memory added | +4.5 MB | +6.5 MB |
| Database queries added | +1 | +1 |
| Hooks registered | +22 | +114 |
<head> bytes added | +4,259 | +2,380 |
| Meta description by default | Yes | Yes |
| JSON-LD types printed | 10 | 0 |
| Open Graph / X tags | 10 / 5 | 10 / 6 |
| Sitemap URLs listed | 72 | 58 |
| Sitemap image entries | 40 | 40 |
lastmod coverage | 72 / 72 | 50 / 58 |
| Custom database tables | 1 (2 with the 404 Monitor on) | 1 |
| Autoloaded options added | +0.4 KB | +3.6 KB |
| Plugin package size | 4.6 MB | 11.7 MB |
| Block editor assets | 2 files, 700.4 KB | 17 files, 217 KB |
| After deactivation | +0.2 KB left autoloading | No reduction at all |
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. Each column heading names the version that was measured. Bold marks the better number in each row. Full method: how we tested.
Hydrogen SEO's figures were measured on 0.0.18 and have not been re-run on later versions. The custom tables row is the exception: it is counted from the 0.0.31 source. A default install has one table, for the internal link counter. Switching on the 404 Monitor, which is off by default, creates a second for its log. Deleting the plugin removes both.
What the numbers mean
On the server, Hydrogen SEO added +12.9 ms and +4.5 MB; SEOPress added +24.5 ms and +6.5 MB. Both added a single query, which is excellent for either. SEOPress registered 114 hooks against Hydrogen SEO's 22 and ships an 11.7 MB package against 4.6 MB. Autoloaded options were small for both: +3.6 KB for SEOPress, +0.4 KB for Hydrogen SEO.
SEOPress's <head> grew by only 2,380 bytes, smaller than Hydrogen SEO's 4,259, and the reason is the schema gap rather than leaner markup: no JSON-LD means fewer bytes. Its meta and social coverage is solid, with 10 Open Graph and 6 X tags against Hydrogen SEO's 10 and 5. If rich results or machine-readable page data matter to you, the missing schema is the largest single output gap either plugin has. SEOPress offers schema in its paid version; we measured free versions only.
Sitemaps favor Hydrogen SEO modestly. Both include featured images (40 entries each). Hydrogen SEO listed 72 URLs, all with lastmod; SEOPress listed 58 and left 8 unstamped. SEOPress also uses /sitemaps.xml rather than the conventional filename, which trips up people checking by hand, though it is declared in robots.txt like every other plugin here.
In the editor, SEOPress is lighter: 17 files totalling 217 KB against Hydrogen SEO's 2 files totalling 700.4 KB, the cost of Hydrogen SEO's React editor UI. Hydrogen SEO's dashboard HTML is smaller (131.2 KB against 185.5 KB). On cleanup, SEOPress creates one custom table and deactivating it released none of its autoloaded options; the Hydrogen SEO version we tested created none and left 0.2 KB (0.0.31 is different: a link-count table by default, plus a 404 log table once its 404 Monitor is enabled, so it no longer has fewer tables than SEOPress). Hydrogen SEO's other difference is its AI layer and agent, which need a free account and are still Beta.
Features: free, paid or not offered
| Feature | Hydrogen SEO 0.0.31 | SEOPress 10.4 |
|---|---|---|
| Search engine verification codes | Free | Free |
| IndexNow instant indexing | Free | Free |
| Redirect manager | Free | Paid |
| 404 monitor | Free | Paid |
| SEO column on the Posts screen | Free | Free |
| SEO fields in Quick Edit | Free | Free |
| Attachment page redirects | Free | Free |
| Author and date archive controls | Free | Free |
| RSS feed text | Free | — |
| max-snippet and preview controls | Free | — |
| Primary category | Free | Free |
| Internal link counts on the Posts screen | Free | Free |
| Automatic image alt attributes | Free | Free |
| Table of contents block | Free | — |
| HTML sitemap | Free | Free |
| Pillar or cornerstone content flag | Free | — |
| Crawl cleanup switches | Free | Free |
| Video sitemap | Free | Paid |
| Google News sitemap | Free | Paid |
| llms.txt | Free | Paid |
This table is not benchmark data. It is based on each plugin's WordPress.org listing, the code of its free version there, and its official documentation and pricing pages, checked on 12 November 2026, for the version in each column heading. Free means the feature is in the plugin's own free version. Paid means it needs that plugin's paid version or a paid add-on. No means the plugin's listing says it does not offer it. A dash means we could not confirm it either way; it does not mean the feature is missing. A row says a feature exists, not how complete it is. Plugins change, so check the plugin's own site before relying on a cell. If a cell is wrong, tell us and we will correct it.
Choose Hydrogen SEO if
- You want schema output from the free plugin: 10 JSON-LD types at defaults.
- You want every sitemap URL stamped with
lastmod(72 of 72). - You want lower PHP time and memory, and a deactivation that leaves 0.2 KB autoloading.
- You want AI help for titles, descriptions and alt text, or an agent for bulk jobs.
Choose SEOPress if
- You want a lighter editor: 217 KB of assets against 700 KB.
- You want a long-established plugin with a restrained, low-upsell admin.
- You manage many client sites and plan to use its paid version, where schema lives.
- You add structured data another way and only need meta, social tags and sitemaps.
Switching between them
Hydrogen SEO's Tools → Import SEO Data detects SEOPress and SEOPress PRO, previews the whole import as a dry run, and brings across templates, robots rules, social settings, per-post fields, PRO redirect rules and SEOPress's per-page redirects, with an Undo in history. Settings saved while a SEOPress module was switched off are treated as not in effect, as SEOPress treated them. Details are in switch from another SEO plugin. SEOPress has its own migration tool for moving in from other plugins; check its documentation for current sources.
Common questions
Does SEOPress output schema markup?
Not at default settings in the free version. On a standard post it printed zero JSON-LD in our benchmark. Hydrogen SEO printed 10 schema types in 2,071 bytes on the same post.
Which is lighter, Hydrogen SEO or SEOPress?
On the server Hydrogen SEO is lighter: +12.9 ms and +4.5 MB against +24.5 ms and +6.5 MB, with one query each. In the block editor SEOPress is lighter, loading 217 KB of assets against Hydrogen SEO's 700.4 KB.
Why does SEOPress use /sitemaps.xml?
It is simply its chosen path. It is declared in robots.txt, so crawlers find it, but submit the correct URL in Search Console. Hydrogen SEO uses /sitemap.xml.