Grammarly Explained: What It Actually Catches (and What It Doesn't)

Grammarly has become the default AI writing assistant for many people, integrated into browsers, email clients, and word processors. Understanding what it's actually checking — beyond "grammar" — helps set realistic expectations for what it will and won't catch.

What it checks beyond basic grammar

Spelling and grammar are the baseline, but Grammarly also flags clarity issues (overly complex sentences), tone (does the writing read as intended — formal, friendly, confident), and increasingly, AI-assisted rewriting suggestions for entire sentences, not just error correction.

Where it's genuinely reliable

Catching typos, basic grammatical errors, and inconsistent punctuation is Grammarly's most dependable function — the kind of error a tired writer misses on their own read-through but a second pass (human or automated) reliably catches.

Where it's less reliable

Tone and clarity suggestions are more subjective and occasionally miss context — a deliberately informal or stylistically unusual piece of writing can get flagged for issues that aren't actually issues. Treating these suggestions as prompts to reconsider rather than commands to follow avoids losing intentional voice in your writing.

What it doesn't do

Grammarly doesn't verify factual accuracy — a grammatically perfect sentence stating something false passes every check cleanly. It's a writing-quality tool, not a fact-checking one, and treating it as the latter is a genuine, common misunderstanding of its scope.

The business use case specifically

For teams producing a lot of external-facing written content — emails, marketing copy, proposals — Grammarly Business adds team style guides and brand tone consistency checking on top of the individual product, worth considering if your team's writing quality varies noticeably by author.

Getting started

Grammarly's free tier covers the core spelling/grammar checking genuinely well — the paid tier's value is specifically in the more advanced tone and clarity suggestions, worth testing on your own real writing before deciding if that upgrade is worth it for your use case.

Using it alongside AI writing tools, not instead of editing

Running AI-generated content through Grammarly catches surface-level errors but doesn't replace a genuine editorial read for accuracy and voice — treating it as one layer in a review process, not the final check, avoids publishing content that's grammatically clean but still says something inaccurate or off-brand.