Analyse comma placement for free
Paste your text into the input field and start the analysis. The tool marks suspicious commas, missing separators and possible false alarms. Accept suggestions only after the sentence test, because for some constructions, such as German infinitive groups, and for differences in meaning, more than one comma placement is possible.
How the AI comma checker works
Our tool checks your text with AI for missing and incorrect commas: before subordinate clauses, relative clauses, lists and insertions, in English and German texts. Paste your text above or upload a file and get the corrected version in seconds.
Do you want to look up the comma rules yourself? You will find all rules with examples in our detailed guide Comma rules and examples. Would you like absolute certainty? Then an experienced proofreader reads every line personally, with our proofreading service from €1.90 per page.
Where automatic checking reaches its limit
Rule-based and AI-assisted checks reliably detect what is clear: commas in lists, after introductory clauses and around relative clauses. It gets difficult where the comma changes the meaning, for example with extended infinitive groups in German.
"Er versprach, ihr zu helfen" and "Er versprach ihr, zu helfen" are both correct in German and mean different things. No tool can decide what you meant to say. This is exactly where human proofreading comes in.
Analyse comma placement reliably
Checking commas with AI is especially helpful where sentence boundaries are clear. This includes subordinate clauses with although, whereas, while or when, relative clauses and many lists. The analysis also often finds a missing second comma when an inserted clause ends. This paired case is easy to overlook when revising: The method, which we chose, suits the question.
The result is still a hint to check and not an automatic approval. A sentence can be grammatically correct and still mean something different. So read the complete sentence before and after each marking. For a long construction, it helps to mark the finite verbs first and to separate the main clause, subordinate clause and insertion from one another.
The most important rule groups for the sentence test
In a list, the comma separates items of equal rank: precise, clear, easy to follow. Before the last item, a comma is optional in British English (the Oxford comma): choose one style and keep to it. In German there is normally no comma when and or or joins the last two items. Contrasting links such as but, yet or however usually take a comma. Two independent main clauses can be separated by a comma before and or or if this makes the text easier to read.
Subordinate clauses are separated from the main clause. If the subordinate clause sits in the middle of the main clause, you need a comma on the left and on the right. The Duden overview of the comma (in German) sorts the rules by lists, additions, subordinate clauses and clause-like groups. For the final check, this division is more helpful than searching for individual signal words.
German texts: infinitive groups with "zu"
In German, extended infinitive groups with zu are generally set off by a comma. The comma is particularly clear after an introduction with als, anstatt, außer, ohne, statt or um. It also applies when the group depends on a noun, adjective, participle or a word that points ahead: Sie hat den Wunsch, früher abzugeben. Erinnerst du mich daran, die Datei hochzuladen?
A simple, unextended infinitive can stand without a comma. In certain constructions the infinitive belongs closely to the predicate and must not be separated. Borderline cases arise, for example, with versuchen, erlauben or versprechen. The Duden guide to infinitive groups without a comma shows why sentence structure and meaning have to be checked there. In such cases a tool should offer a decision but not force a single variant as certain.
Commas that change the meaning
Sometimes a comma does not just mark off a form but changes what belongs together. Let's eat, Grandma and Let's eat Grandma are not the same statement. With additions too, the separation decides whether information is read as restrictive or as an afterthought. That is why the question What is meant to belong together? matters just as much as looking for a signal word.
A common false alarm involves short insertions and set phrases. Some groups may be set off with commas but do not have to be. Then check whether two commas form a pair. If only the first is set, the supposed correction often creates a new error.
Direct speech, address and added remarks
Outside classic subordinate clauses there are also fixed separations. A form of address is separated from the rest of the sentence by a comma: Ms Meier, please check the attachment. This also applies to short forms of address at the start or end of a sentence. In German direct speech, a comma separates the speech tag when the quoted sentence ends with a question mark or exclamation mark: „Ist die Fassung fertig?“, fragte sie.
Added explanations are set off as well. These include additions with in other words, especially, that is, in particular or namely, when they appear as a separate afterthought. What matters is not the signal word alone but its function in the sentence. Read the sentence once without the addition: if the core sentence stays grammatical, that speaks for setting it off.
How to judge a suggestion from the check
Do not accept a comma marking in isolation. First name the rule group, then find the two units that are to be separated, and finally check the meaning. If you cannot assign a rule, open the matching rule page and compare an example built in the same way. In this way the comma check becomes a learning tool: you do not just take over a correction, you can justify it yourself in the next sentence.
A controlled process for longer texts
- Check the text section by section so that the sentence context is preserved.
- Deal with clear subordinate clauses and lists first.
- Then check every pair of commas around insertions and relative clauses.
- Judge infinitive groups with a view to dependence and clause-like status.
- Read the revised version aloud and compare it with the intended message.
For a single rule, you will find more precise decisions in the overview of comma rules with examples and on the linked special pages. Anyone who checks commas with AI gets a quick first pass. For academic work or publications, a final human check remains sensible, because besides the rule it also assesses meaning, style and consistency.