Why does the checker report a lower-case word after a full stop?

Because that is the pattern of an unfinished edit. The rule looks for a terminator followed by a lower-case word and ignores abbreviations such as e.g. and initials such as J.K., so ordinary academic prose does not trip it.

Why are country names not checked here?

They are the Proper Noun Checker's responsibility by design. That tool holds the documented place-name list and also finds a name the document writes in two different forms, which a case-only rule cannot do.

Is writing in all capitals a mistake?

Not necessarily, which is why it is reported as style. Emphasis, initialisms and headings are all legitimate uses. The published acronym list keeps the everyday initialisms quiet so the remaining findings mean something.

Why was the word iPhone not corrected?

Because the internal capital is part of the brand name. A list of known brand forms — iPhone, macOS, YouTube, GitHub, JavaScript, eBay and others — is exempt from the check, so the rule never rewrites a name that is correct.

Does it fix the text automatically?

No. Each finding shows the word as written and the suggested form, and the draft is never modified. The exemption lists and the rule list are both on the page, so every silence and every finding can be accounted for.

Capitalization Checker

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What is checked, and what is left alone

The 5 checks are: a lower-case word after a full stop, question mark or exclamation mark (a lower-case start of the text or of a line counts too); the pronoun "i" written lower-case, including i'm and i've; a lower-case day, month, language or nationality; a word in ALL CAPS; and a capital inside an ordinary word.

Two of the five are style, not error. ALL CAPS can be deliberate emphasis and a capital inside a word is often part of a brand, so both are reported with a style severity. The acronym allowlist covers the everyday ones (API, URL, JSON, PDF, SEO, CEO, USA), and brand names such as iPhone, macOS, YouTube and GitHub are never rewritten.

Names that are also ordinary words are never flagged on their own: "I may go in march", "we polish the table" and "an august evening" all stay clean. Abbreviations (e.g., i.e.) and initials (J.K.) do not count as sentence ends, and a deliberate lower-case start after an ellipsis is left alone.

Country, continent and planet names are the Proper Noun Checker's job, because that tool also looks for a name written two different ways. This checker handles the names that follow a plain case rule.

This capitalization checker runs five published checks — lower-case sentence starts, the pronoun i, day, month, language and nationality names, ALL-CAPS words and capitals inside a word — and keeps the two style checks separate from the errors.

What is Capitalization Checker?

Capitalization errors are quiet ones. A lower-case word after a full stop does not look wrong in a paragraph of ordinary sentence case, which is why it survives a careful read and why a mechanical scan is worth running. This capitalization checker runs five checks, publishes all five, and separates the two it treats as style from the three it treats as errors.

The sentence-start check looks for the error itself: a full stop, question mark or exclamation mark, then a lower-case word. Reading the pattern rather than the parsed sentences is deliberate, because the shared sentence splitter needs a capital to recognise a sentence boundary at all, and a lower-case start would be invisible to it. A lower-case first word of the text, or of a new line, counts as well. Two carve-outs keep it quiet on academic prose: abbreviations such as e.g. and i.e. do not end a sentence, and initials such as J.K. do not either. A deliberate lower-case start after an ellipsis is left alone, because that pattern is a style choice in fiction and dialogue.

The pronoun rule finds a lower-case i standing alone and inside its contractions — i, i'm, i've, i'll, i'd — while staying out of i.e. and other abbreviations that merely begin with the letter. The name rule holds 81 day, month, language and nationality names and reports a lower-case list of the names itself. The long weekday and month names are read from the platform's Intl data at run time rather than typed into the engine, so the rule cannot drift from the names the browser actually prints.

The fourth and fifth checks are style. A word in ALL CAPS is reported unless it is on the published acronym list — API, URL, JSON, PDF, SEO, CEO, USA and their relatives — because emphasis and initialisms are both legitimate and a wall of capitals is a habit rather than a fault. A capital inside a word is reported unless the word is a known brand: iPhone, macOS, YouTube, GitHub, JavaScript and eBay are never rewritten, and the tool has no opinion about a name it does not recognise beyond listing it.

Scope matters here, and the page states it. Country, continent and planet names belong to the Proper Noun Checker, because that tool also looks for a name the document writes two different ways, which is the more useful question for a repeated name. Names that are also ordinary words — march, may, august, polish — are never flagged on their own in either tool, because a sentence about a march or a polish is not a sentence about a month or a country.

Use the counts to see which habit the draft has. A single digits-only number under one rule is one fix; a spread across the style rules usually means the draft needs a decision about emphasis rather than a tidy-up. Copy report and Download produce the findings with the suggested form for each, so the fixes can be made in one pass.

How to use Capitalization Checker

Paste your text; all five checks run as you type and each count appears in the grid.
Work through the sentence-start findings first — they usually cluster around one editing seam.
Check the pronoun i findings, including contractions that begin a clause.
Read the ALL-CAPS findings as a style question: keep the ones that are deliberate emphasis.
Send country, continent and planet issues to the Proper Noun Checker, which owns them.

When to use Capitalization Checker vs related tools

Use this checker on any draft that has been edited in pieces, since a lower-case sentence start is usually the scar of a rewrite. Where the capitalisation problem is a name written two ways, the Proper Noun Checker handles it with a documented lexicon and an inconsistency check.

When the capital is right but the mark beside it is not, the Punctuation Checker covers unmatched brackets, doubled marks and a paragraph with no full stop, and the Grammar Checker adds its own sentence-level checks over the same text.

Privacy & Security

This tool runs entirely in your browser — no data ever leaves your device. There is no server round-trip, no upload, no logging, and no account required. Your input is processed locally using client-side JavaScript and is never stored, transmitted, or accessible to anyone else. When you close the tab, everything disappears.