Should you build or buy Writing Assistant & Proofreading?

Writing assistant and proofreading tools check grammar, spelling, clarity and tone inside a browser, document editor or email client, and often layer a company style guide on top. Anyone who writes for work, individually or across a whole organization with an admin console, buys these to catch errors and keep prose readable before it ships.

The correction is commodity LLM work; a seat is worth paying for only if the in-flow integration and governance matter.

Build it, buy it, or bridge?

⚒ Build it
✓ Buy it
➔ Bridge
Cost shape
General-purpose LLMs already do this work; the marginal cost of a rewrite is a fraction of a cent per document.
Grammarly Pro runs $144 a year per member, billed annually, cheap next to most software line items.
Use an LLM you already pay for to draft and correct; keep Grammarly only for its in-flow browser checker.
Time to value
Pasting into an LLM you already have access to works today, with zero setup for an individual writer.
Grammarly and ProWritingAid install once and correct inline across nearly every app an employee types in.
Start with an LLM for drafting; add the inline checker once the team needs consistent cross-app coverage.
Differentiation captured
Clean prose confers no edge; no company wins customers because its emails had fewer typos.
The admin console, style guide enforcement and usage analytics are the whole reason to keep paying.
Own nothing distinctive in the correction itself; pay only for the governance layer wrapped around it.
AI feasibility today
Large language models handle grammar, clarity and tone correction well enough that AI commoditized this job first.
Grammarly's own product is now an LLM-based assistant, not a rules engine, competing with the general models it's built on.
Draft and rewrite with any capable LLM; keep a dedicated checker only for its admin controls and style guide.
Who it fits
Anyone with access to a capable LLM and no need for cross-app governance or a shared style guide.
An organization that wants a consistent style guide enforced automatically across every employee's browser and inbox.
A team that drafts with an LLM but still wants centralized visibility into tone and terminology compliance.

When building makes sense

Proofreading was one of the first tasks large language models got genuinely good at, and using one instead of a dedicated grammar checker costs close to nothing per document once a team already has LLM access through a subscription it pays for anyway. LanguageTool's core engine is open source, and anyone can set up their own LanguageTool server locally or in the cloud, so a team that wants to run its own grammar and style checks without any vendor relationship has a real, documented path to do that. What neither option fully replaces is the always-on layer: a checker that runs inline across every browser tab, document editor and email client an employee touches, with a central admin console that enforces one company style guide and reports on usage. Building earns its keep for an individual writer or a small team with no need for that cross-app governance, not for an organization trying to enforce consistent tone at scale.

When buying makes sense

Buying is really about the integration layer, not the correction itself, because the underlying grammar and tone work is now commodity AI. Grammarly Pro costs $144 a year per member on the annual plan, which works out to $12 a month, a modest price for a checker that runs inline across nearly every browser tab, document and email an employee opens, with a shared style guide and usage analytics an admin can actually see. That in-flow coverage across every app is the piece a general-purpose LLM doesn't replicate on its own; pasting into a chat window works for one document at a time, not for catching a typo mid-sentence in a Slack message. The buy case is strongest for an organization that wants one enforced style guide and centralized visibility into how consistently people are writing, not for an individual who's happy pasting into an LLM they already have.

The desk read

Build-versus-buy analysis for Writing Assistant & Proofreading is being written. In the meantime, the framework that drives every B4 call is on the B4 Index page.

Representative vendors GrammarlyLanguageTool + 5 more, listed in the full index

Frequently asked

What do writing assistant and proofreading tools actually do?

A grammar and style checker that runs inline while someone writes, catching typos, awkward phrasing and off-brand tone before a message or document goes out, rather than after someone else spots it. The category exists because catching the error while someone is still typing beats catching it after the fact, whether the checker is a browser extension or a large language model plugged into the same text box.

Can a general AI chatbot really replace Grammarly?

For the correction itself, largely yes; rewriting and tone adjustment are core large-language-model capabilities now. What a chatbot doesn't do on its own is run inline across every app you type in with a shared admin console, which is the specific thing an organization is paying Grammarly for.

Is there a real open-source alternative to a paid grammar checker?

Yes. LanguageTool's core engine is open source, and anyone can set up their own server locally or in the cloud rather than relying on the hosted product. It covers grammar and style checking without a per-seat license, though it lacks some of the always-on browser integration the paid product ships.

How much does Grammarly Pro actually cost?

$144 a year per member on the annual plan, which works out to $12 a month; monthly billing runs $30 and quarterly $60. Grammarly has folded its old Business plan into Pro, so the enterprise-style admin features now live under that same name.

What are the main writing assistant vendors?

Representative vendors include Grammarly, LanguageTool. B4 Pro includes the category score and the full vendor list.

The B4 Index scores every software category on two axes, strategic differentiation and AI feasibility, to classify it Build, Buy, Bridge, or Beware. See the full methodology.

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