Hydrogen SEO: The WordPress SEO Plugin to Use While You Wait

Disclosure. Sheesh Labs builds both Hydrogen SEO and RankWave AI, so read this page as a builder's view, not a neutral review. Every number below comes from the Hydrogen SEO benchmark, which Hydrogen SEO did not win overall.

What it is

Three pieces: a free plugin, a Pro plugin and a SaaS.

The full WordPress.org name is "Hydrogen SEO – AI SEO Plugin for Schema, Sitemaps, llms.txt & AEO". Requires WordPress 6.7+, tested up to 7.1, PHP 7.4+, GPLv2 or later. It is Beta software; that is a real caveat, not false modesty.

Free · v0.0.20

The WordPress plugin

Titles, meta, schema, sitemaps, llms.txt, robots, redirects, canonicals, audits and a site health score. Zero front-end JavaScript, no custom database tables, REST API, WP-CLI, filters and actions. Block editor, Elementor and Divi supported.

Install guide →

Pro · v0.0.3

Hydrogen SEO Pro

Activated with a licence key from a hydrogenseo.com account, one key per site, movable. Adds bulk AI meta for up to 500 posts, schema autopilot across post types, content scoring against a target query, llms.txt and AEO monitoring inside wp-admin, priority support and automatic updates.

Pricing →

hydrogenseo.com

The SaaS

Single-URL audits ranked by estimated traffic impact with the fix written out, bulk audits up to 5,000 URLs, a schema generator, an AI-visibility monitor for ChatGPT, Perplexity and AI Overviews, competitor comparison, Core Web Vitals and an API with scoped keys.

Platform overview →

Free vs AI

What works with no account, and what needs one.

Every non-AI feature works with no account and no key. Only AI features need a free hydrogenseo.com account. Plans differ in AI credits and number of sites, never in features. When credits run out, only AI generation pauses; nothing else breaks.

Free plugin, no account	Needs a free account (AI)	Pro plugin adds
SEO titles and meta descriptions with template variables for posts, pages, custom post types, taxonomies and archives	AI meta titles and descriptions: several suggestions with character counts, on six fields (SEO title, meta description, OG title and description, X title and description)	Bulk AI meta for up to 500 posts at once
JSON-LD schema: Article, Product, FAQ, HowTo, Recipe, Course, Event, Local Business, Breadcrumbs and more	AI-assisted schema	Schema autopilot across post types
XML sitemaps with images and lastmod; robots meta per post; robots.txt editor; llms.txt editor	AI image alt text, single or bulk across the media library	llms.txt and AEO monitoring inside wp-admin
Open Graph and X card previews, Google SERP preview, canonical URLs, homepage SEO, 301/302 redirection manager	AI content generation and rewriting; AI featured image generation	Content scoring against a target query
Site health score across 7 areas; audits for duplicate titles and descriptions, keyword cannibalisation, orphan pages, broken internal links, too-long or too-short metadata	Hydrogen AI agent: plain-language jobs across 87 abilities	90 abilities, priority support, automatic updates
One-click import from seven other SEO plugins; REST API; WP-CLI; filters and actions	1,000 AI credits on signup, no card	20,000 (Pro) or 50,000 (Max) AI credits a year

The full feature list lives in the Hydrogen SEO introduction; the credit rules are in credits and billing.

The agent

Hydrogen AI asks before it acts.

Hydrogen AI takes plain-language jobs such as "write meta descriptions for every post missing one", "add FAQ schema to this page" or "find and fix broken internal links". It works through the plugin's own registered abilities (the WordPress Abilities API): 87 in the free plugin, 90 with Pro.

It lives in the plugin dashboard for site-wide jobs and in the editor's SEO sheet for one post. It cannot act until AI Abilities is switched on and connected. Full write-up in Meet Hydrogen AI and on this site in SEO Agent vs SEO Tool.

Asks before anything it cannot undo, shows every change, and can be stopped mid-job.
Three policies: confirm destructive only, confirm every write, or read-only.
Revocable WordPress application password for access; the site key never reaches the browser.
Backend: a LangGraph agent loop behind a fixed 10-tool interface (search_tools, describe_tool, run_tool) that reaches abilities as data, so the prompt cache stays stable.
Safety notes in AI abilities and safety; worked examples in agent recipes.

Measured performance

Third on PHP time and memory. Not first.

Sheesh Labs benchmarked seven SEO plugins on the same rig: WordPress 7.1, PHP 8.2.27, MySQL 8.0.35, Twenty Twenty-Five, 40 posts and 8 pages, one plugin active at a time, database restored between runs, 6 warm-up and 13 measured requests, median reported. Baseline with no SEO plugin: 53.9 ms PHP, 38 MB, 35 queries. Re-run on 8 September 2026.

Plugin (version)	PHP time	Peak memory	Queries	Package	Custom DB tables
The SEO Framework 5.1.4	+8.0 ms	+2.0 MB	+0	2.9 MB	0
Slim SEO 4.10.1	+10.0 ms	+2.0 MB	+2	1.4 MB	0
Hydrogen SEO 0.0.18	+12.9 ms	+4.5 MB	+1	4.6 MB	0
SEOPress 10.2	+24.5 ms	+6.5 MB	+1	11.7 MB	1
Rank Math 1.0.278	+36.1 ms	+8.5 MB	+16	15.1 MB	6
Yoast SEO 28.4	+39.0 ms	+10.5 MB	+3	21.0 MB	6
All in One SEO 5.0.1.1	+53.5 ms	+14.5 MB	+22	24.4 MB	9

Cost added versus baseline, lower is better. Source: Which WordPress SEO Plugin Is Actually the Best? We Tested All 7 and Measured Everything (Hydrogen SEO, re-run 8 Sept 2026). Method: benchmark method. Sheesh Labs builds Hydrogen SEO.

The SEO Framework won or shared 7 of 16 categories and Slim SEO 5. Hydrogen SEO won "most efficient schema" (10 JSON-LD types in 2,071 bytes on a standard post), tied on zero custom database tables, and shipped a sitemap with full lastmod and images (72 URLs, 40 images, 72 of 72 lastmod). It placed third on PHP time and memory and second on queries and autoloaded options. All seven plugins add 0 front-end files, 0 KB and 0 inline JS.

The bug they published. The first run of this benchmark found Hydrogen SEO 0.0.14 printed no canonical tag at all; bare WordPress did better. 0.0.15 fixed it with one central canonical output for every context, cut settings reads from +7 queries to +1 (+0 once settings are saved), and shrank the package from 5.5 MB / 683 files to 4.6 MB / 322 files. 0.0.16 shipped security fixes. The post went out with the bug in it and was re-run afterwards. Our take on this site: What Is the Fastest WordPress SEO Plugin?

Switching

One-click import from the plugin you already use.

Tools → Import SEO Data reads your existing plugin and brings across title and description templates, robots rules, homepage SEO, social defaults, knowledge graph, robots.txt, per-post and per-term SEO fields, focus keywords, canonicals, schema type and redirect rules. Smart tags are translated to Hydrogen SEO's template variables.

Supported sources: Rank Math (and PRO), Yoast SEO (and Premium), SureRank (and Business), All in One SEO (free and Pro), The SEO Framework, Slim SEO (and Pro), SEOPress (and PRO). Shipped in 0.0.19 and 0.0.20.

Switch from another SEO plugin Rank Math alternatives →

Dry-run preview before anything is written, so you see the exact result first.
Batches with pause and resume, for large sites.
Undo from history. Nothing from the old plugin is deleted.
Optional deactivation of the old plugin once you are satisfied.
WP-CLI: wp hydrogen-seo migrate run rank-math --dry-run

Pricing summary

Free forever. Paid plans buy credits, not features.

Prices from hydrogenseo.com/pricing, September 2026. One credit is one single-URL audit; image generation costs 3 credits, alt text 1, content 2.

Free

$0 forever

1,000 AI credits on signup, no card. The free WordPress plugin, with every non-AI feature and no account needed for them.

Pro

$99 / year

was $149 · or $399 lifetime (was $599)

20,000 AI credits a year, the Pro plugin and automatic updates.

Max

$179 / year

was $249 · or $799 lifetime (was $999)

50,000 AI credits a year. Same features as Pro; more credits and sites.

Full pricing on hydrogenseo.com What AI SEO actually does for WordPress →

Start here

Four docs that cover the first afternoon.

FAQ

Hydrogen SEO, asked plainly.

Is Hydrogen SEO free?

Yes. The Hydrogen SEO WordPress plugin is free on WordPress.org and every non-AI feature works with no account and no key. AI features need a free hydrogenseo.com account, which comes with 1,000 AI credits. Paid plans (Pro from $99 a year, Max from $179 a year) add more credits and sites; they never gate features.

Is Hydrogen SEO stable enough to use on a live site?

Hydrogen SEO is Beta software at version 0.0.20, and Sheesh Labs says so plainly. The 0.0.14 release shipped without a canonical tag; 0.0.15 fixed it and 0.0.16 shipped security fixes. Fixes ship with version numbers. Try it on a staging site first if you can, and keep the dry-run import until you are happy. Our Hydrogen SEO review goes through the caveats.

Does Hydrogen SEO slow down a WordPress site?

In the Hydrogen SEO benchmark re-run on 8 September 2026, Hydrogen SEO 0.0.18 added 12.9 ms of PHP time, 4.5 MB of memory and 1 query on a standard post, placing third behind The SEO Framework and Slim SEO and well ahead of SEOPress, Rank Math, Yoast SEO and All in One SEO. It adds zero front-end JavaScript and no custom database tables.

Can I import my settings from Rank Math or Yoast SEO?

Yes. Tools → Import SEO Data brings titles and description templates, robots rules, homepage SEO, social defaults, per-post and per-term fields, focus keywords, canonicals, schema type and redirect rules from Rank Math, Yoast SEO, SureRank, All in One SEO, The SEO Framework, Slim SEO or SEOPress. It previews as a dry run, runs in batches, can be paused, and can be undone from history. Nothing is deleted. See switch from another SEO plugin.

Do I need a hydrogenseo.com account to use the plugin?

No. Titles, schema, sitemaps, llms.txt, robots, redirects, canonicals, audits and the import tool all work with no account and no key. A free account is only needed for AI features: AI titles and descriptions, alt text, content tools, AI schema and the Hydrogen AI agent. If AI credits run out, only AI generation pauses; nothing else breaks. Details in connect your account.