What a Grammar Checker Catches and Misses

A grammar checker is a second pair of eyes that never gets tired. It is very good at some mistakes and blind to others. Knowing the difference tells you when you can trust the green tick and when a human read is still needed.

How our checker works

The Grammar and Spelling Checker is a rule-based tool, not an AI writing assistant. It does two things:

1. Spelling. Words are checked against a standard English (US) dictionary, and unknown words are flagged with suggestions.
2. Written rules. A set of patterns finds common mistakes.

Each issue is shown in context, with a one-click fix. You can accept suggestions one at a time or apply them all and copy the corrected text. It handles up to 30,000 characters at a time. Your text stays in your browser.

What it catches

The checker looks for specific, well-defined patterns. These are real results from the tool on example sentences:

It also flags missing capital letters at the start of a sentence, stray extra spaces and spaces before commas, and misspelled words that are not in the dictionary. The same patterns work for "could of" and "would of", and for "a" and "an" before the wrong kind of sound, such as "a honest man".

These errors have clear, checkable patterns, which is why a tool is reliable on them. It matches the patterns it knows, not every possible case.

What it misses

• Wrong word that is a real word. If you write "form" for "from", the dictionary sees a valid word.
• Look-alike words outside its patterns. The checker flags "Its a" but not "The company raised it's prices", and it flags "Your welcome" but not "Their going to the park" or "They forgot there keys". Mix-ups of its/it's, their/there/they're and your/you're are only caught in the phrases it knows.
• Awkward or unclear phrasing. A sentence can be grammatical and still confusing.
• Style and tone. Whether a sentence suits your reader is a human judgement.
• Logic and facts. A tool does not know that a date or a total is wrong.
• Subtle grammar. Subject-verb agreement across long sentences and misplaced modifiers are hard for simple rules.
• Names and technical terms. They may be flagged although they are correct, and your own words may be missing from the dictionary.
• Other languages and regional spelling. It checks English only, against US spelling.

Spelling variants and language

The checker uses a standard English (US) dictionary. British, Canadian and Australian spellings such as colour, organise or centre may be flagged even though they are correct in your country, so choose one spelling convention and stay with it throughout a document. Names, brand names, abbreviations and words from other languages are also likely to be flagged. Ignore those, and add nothing to the text just to silence a flag.

A proofreading routine that works

1. Write first, edit later. Do not stop to fix every word while drafting.
2. Run the checker and fix real errors. Ignore flags on names and specialist terms.
3. Read aloud. Awkward phrasing and missing words are easier to hear than to see.
4. Change the view. Print it, or change the font and size, so your eyes do not skip the familiar.
5. Check the numbers, names and dates against the source.
6. Take a break before the final read. Fresh eyes catch more.

Length and structure

A checker does not care about length, but readers do. The Word Counter measures it, and how long should it be? gives typical lengths. To shorten a long draft, try the Text Summarizer to see which sentences carry the point. If your drafts are for a CV, the Resume ATS Checker looks at structure and keywords, which grammar rules do not.