How to Use This Tool
A comma splice is two complete sentences joined with nothing but a comma. It is the single most marked punctuation error in academic writing, and it is invisible to spellcheckers because every word is spelt correctly and the sentence reads perfectly well aloud.
The experiment failed, we repeated it the following week. Both halves could stand alone. A comma is not strong enough to hold them together.
The four repairs
- Full stop. Always correct, never elegant. Use it when in doubt.
- Semicolon. Use when the two statements are closely related and you want to signal that. The experiment failed; we repeated it.
- Add a coordinating conjunction after the comma. There are exactly seven, remembered as FANBOYS: for, and, nor, but, or, yet, so. With one of these the comma becomes correct.
- Subordinate one clause. Because the experiment failed, we repeated it. This is usually the strongest fix, because it states the relationship instead of leaving the reader to infer it.
The however trap
This is the one worth learning, because it catches strong writers. However, therefore, moreover, consequently, nevertheless, thus, hence, instead and furthermore are conjunctive adverbs, not conjunctions. They cannot join two clauses, so a comma before them produces a splice every time.
Results were inconsistent, however the team published anyway. — wrong.
Results were inconsistent; however, the team published anyway. — correct.
How the detection works, and where it fails
This is a heuristic, not a grammar parser. Deciding with certainty whether a comma joins two independent clauses needs syntactic analysis, which is not something a page like this can do honestly. Instead it looks for two patterns:
- Comma followed by a conjunctive adverb. Very reliable — marked as a likely splice.
- Comma followed by a subject pronoun and a probable verb. Good but not perfect — marked as worth checking.
It will miss splices where the second clause starts with a noun phrase (The tests failed, the team regrouped), because distinguishing that from a list or an appositive needs a parser. It will occasionally flag correct writing, particularly non-restrictive clauses and some inverted constructions.
Treat every result as a prompt to look, not a verdict. Read the sentence and ask the only question that matters: could each half stand alone as a sentence? If yes, and there is only a comma between them, it is a splice.
When a splice is acceptable
In fiction and journalism, deliberately, for pace: I came, I saw, I conquered. Three short parallel clauses read as one breath, and every style guide allows it. In academic writing, an exam essay or a professional report, do not. The marker has no way to tell your stylistic choice from an error, and will assume the error.
Nothing is uploaded
The analysis runs in your browser. Nothing is transmitted, which matters when the text is an unpublished paper or a graded assignment.
