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Documentation · head to head

Fumadocs vs Grammarly

Fumadocs logo

Fumadocs

Documentation

Documentation framework for Next.js that treats the docs site as an application rather than a static export

From
Free
Rated
-
Full reviewWebsite
Grammarly logo

Grammarly

Documentation

Great writing, simplified

From
Free
Rated
-
Full reviewWebsite

The short version

  • Each has a real cost: Fumadocs it is a library rather than a finished theme, so the initial setup is meaningfully longer than a generator that ships a working site from one command.; Grammarly occasional false positives and grammatically incorrect suggestions that can introduce errors
  • They diverge on capability: Fumadocs covers Next.js App Router native, Grammarly covers Grammar checking.
  • Prices and features above were last checked on 31 August 2026.

Where they differ

Only the attributes on which Fumadocs and Grammarly actually diverge.

Attributes where Fumadocs and Grammarly differ
AttributeFumadocsGrammarly
Pricing modelOpen source, no licence feeUnknown
PlatformsWeb, macOS, Windows, LinuxWeb, macOS, Windows, iOS, Android
FoundedUnknown2009

Identical on both: starting price (Free), free tier (Yes), user rating (Not yet rated), category (Documentation).

What each one covers

Drawn from each product's published feature list. An absence here means we hold no record of it - not that the product lacks it.

Only in Fumadocs

  • Next.js App Router native
  • Multiple content sources
  • OpenAPI page generation
  • Built in search
  • Headless and styled layers
  • Type safe frontmatter
  • Code and content colocation

Only in Grammarly

  • Grammar checking
  • Spelling correction
  • Punctuation
  • Clarity suggestions
  • Engagement feedback
  • Delivery insights
  • Plagiarism checker
  • Citation generator

What people use each for

The jobs each tool is most often brought in to do.

Fumadocs

  • Documentation that must sit behind login and show different content to different customer plansnot Grammarly
  • A Next.js product team that wants docs to deploy in the same pipeline as the applicationnot Grammarly
  • API reference pages generated from an OpenAPI document alongside hand written guides in one navigation treenot Grammarly
  • A design system site where the component documentation must render the live components from the same codebasenot Grammarly

Grammarly

  • Email writingnot Fumadocs
  • Document editingnot Fumadocs
  • Academic writingnot Fumadocs
  • Business communicationnot Fumadocs
  • Content creationnot Fumadocs

Where each one falls short

Documented limitations, not opinions. Every one is a constraint you would hit in normal use.

Fumadocs

  • It is a library rather than a finished theme, so the initial setup is meaningfully longer than a generator that ships a working site from one command.
  • Maintenance is concentrated in a very small group, so an unresponsive week is a blocked upgrade and there is no support contract to escalate to.
  • It only targets Next.js, so adopting it commits the documentation to that framework and a later migration means rewriting the site rather than swapping a theme.
  • Breaking changes have arrived across minor versions during rapid development, so pinning versions and reading migration notes is a recurring cost rather than a one off.
  • Running docs inside the application means docs traffic hits your application infrastructure and shares its failure modes, where a separate static site would have stayed up.

Grammarly

  • Occasional false positives and grammatically incorrect suggestions that can introduce errors
  • Privacy concerns about sending text to Grammarly's servers for analysis
  • AI capabilities sometimes produce hallucinations and fabricated citations that appear grammatically correct

Pricing, plan by plan

Fumadocs

Free
  • Open sourceFree
    • MIT licence
    • All packages included
    • Self hosted or deployed with your Next.js application

Grammarly

Free
  • FreeFree
    • Basic grammar and spelling checks
    • Tone visibility
    • 100 AI prompts per month
  • Pro$12/month
    • Sentence rewrites
    • Tone adjustment
    • Plagiarism and AI detection

Which should you pick?

Choose Fumadocs if

  • You need next.js app router native.
  • You want to start without paying.
  • You work on Web, macOS, Windows, Linux.
  • You also want multiple content sources.
Fumadocs review

Choose Grammarly if

  • You need grammar checking.
  • You want to start without paying.
  • You work on Web, macOS, Windows, iOS, Android.
  • You also want spelling correction.
Grammarly review

Questions people ask

Is Fumadocs or Grammarly better?
Neither clearly leads. Fumadocs starts at Free and Grammarly at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Fumadocs or Grammarly?
Fumadocs starts at Free and Grammarly at Free.
Does Fumadocs or Grammarly run on more platforms?
Fumadocs runs on Web, macOS, Windows, Linux. Grammarly runs on Web, macOS, Windows, iOS, Android.
Can I use Fumadocs for free?
Both have a free tier, so you can try either at no cost before committing.
What is Fumadocs best used for?
Fumadocs is most often used for documentation that must sit behind login and show different content to different customer plans, a next.js product team that wants docs to deploy in the same pipeline as the application, api reference pages generated from an openapi document alongside hand written guides in one navigation tree, a design system site where the component documentation must render the live components from the same codebase. Of those, documentation that must sit behind login and show different content to different customer plans and a next.js product team that wants docs to deploy in the same pipeline as the application are not what Grammarly is typically brought in for.
What can Fumadocs do that Grammarly cannot?
Fumadocs covers Next.js App Router native, Multiple content sources, OpenAPI page generation, Built in search. Grammarly covers Grammar checking, Spelling correction, Punctuation, Clarity suggestions.

Answered from the vendors’ own pages

Fumadocs: Can I put documentation behind authentication?

Yes. Pages are Next.js server components, so the same session and authorisation checks the rest of the application uses apply.

Grammarly: Does Grammarly have a free version?

Yes, Grammarly offers a free tier with basic spelling, grammar, and punctuation checks, tone visibility, and 100 AI prompts per month. The Pro plan ($12/month annual) adds sentence rewriting, plagiarism detection, and 2,000 AI prompts.

Source
Fumadocs: Does it work outside Next.js?

No. The UI layer depends on the Next.js App Router.

Grammarly: What platforms does Grammarly work with?

Grammarly works across 1 million+ apps including Google Docs, Microsoft Word, Outlook, Slack, Gmail, and web browsers. It also integrates with productivity tools like Asana, Jira, Monday.com, Confluence, and HubSpot.

Source
Fumadocs: Can it generate pages from an OpenAPI spec?

Yes, including operation pages, schema rendering and an interactive request playground.

Grammarly: Can I use Grammarly offline?

Grammarly requires an internet connection to function, though the browser extension works with some offline text areas. For offline use, the desktop app and browser extensions sync when reconnected.

Source
Fumadocs: Who maintains it and is that a risk?

A very small maintainer group. For a long lived commercial documentation set, treat the low bus factor as a real risk and budget for owning a fork.

Grammarly: What is included in the Enterprise plan?

The Enterprise plan includes unlimited team members, dedicated support, custom roles and permissions, data loss prevention, bring-your-own-key encryption, and unlimited AI prompts. Pricing is custom and available by contacting sales.

Source
Fumadocs: Do I still need a separate docs deployment?

No, and avoiding one is the main reason to choose it. The cost is that docs share your application uptime.

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