What the Citation Coverage Checker does
This checker maps the citations in a piece of text to its sentences and its reference list: it finds factual-looking sentences with no citation, markers such as [5] that point at no reference, references that are never cited, numbers cited out of order, and references with no URL or DOI. It maps; it never opens a source or judges whether a source supports its sentence.
It suits AI-generated answers, which often invent a next reference number or cite a list that does not match the text, as well as reports, articles and assignments with numbered references. Everything runs in your browser.
How to use it
- Paste the text with its reference list at the end, under a heading such as References or Sources, or as a trailing block of [n] lines. You can also paste the list into its own box.
- Press Check citations. Numbered markers ([1], [2, 3], [4-6]), footnote markers ([^note]), Markdown links and bare URLs are recognised.
- Read the coverage figure and the findings, then the sentence table: every sentence is marked cited, uncited, not factual or broken marker.
- Download the table as CSV, copy the uncited sentences to send back for sourcing, or download the full map as JSON.
Reading the results
Coverage is the share of factual-looking sentences that carry at least one citation. A sentence counts as factual-looking when it contains checkable detail - a number, date, quotation, attribution or superlative - by the same A2Z heuristic as the claim extractor.
A missing reference (a marker with no entry) is an error: the reader cannot follow it, and in AI output it often means the citation was invented. An unused reference is a warning: it may belong to text that was cut.
Out-of-order numbering only matters for numeric styles such as Vancouver and IEEE that number references by first appearance.
Worked example: an AI answer about hybrid working
The example answer has seven sentences and a list of four references. Six sentences look factual; five of them carry a marker, so coverage is 83%.
"Employees save an average of 72 minutes a day by not commuting" has no citation. "Most managers now prefer hybrid schedules [5]" cites a reference that does not exist - the list stops at [4]. Numbering is also out of first-appearance order ([5] appears before [4]), and reference [4], the Centre for Cities tracker, has no URL or DOI.
The closing sentence, "It is a big change for city centres", has no checkable detail and is not counted. Note what the check cannot tell you: whether the NBER paper really says remote work rose after 2020, or whether the ONS figure is 28%. That is still a job for a person with the sources open.
Formulas and scoring rules
- Coverage
coverage = cited factual sentences / all factual-looking sentencesShown as a whole percentage. Sentences with no checkable detail are left out of both counts.
Limitations: what the result does not prove
- It never opens a reference and cannot tell whether a source exists, is reliable, or supports the sentence that cites it. A fully cited text can still be wrong.
- Author-date styles such as (Smith, 2021) are not parsed as markers; numbered, footnote and link citations are.
- Which sentences count as factual is an A2Z heuristic; common knowledge may be flagged and some claims without signal words may be missed.
- A citation at the end of a paragraph is attributed to the sentence it follows, not to the whole paragraph.
Privacy: where your data goes
Everything you paste, type or drop is processed in this browser tab. It is not uploaded, logged, stored or sent to analytics. Session recording and tag-manager scripts are switched off on this page.
Standards and sources
- NLM - Citing Medicine (Vancouver style numbering)
- IEEE Reference Guide
- Liu et al. - Evaluating verifiability in generative search engines
Frequently asked questions
How do I check whether AI citations are real?
First map them: every marker should resolve to a reference, and every reference should have a URL or DOI you can open - this tool does that part. Then open each source and confirm it exists and says what the sentence claims. Invented references often have plausible titles but no working link.
What does citation coverage mean?
The share of statements that need a source and actually have one. Here it is the proportion of factual-looking sentences - those with numbers, dates, quotations, attributions or superlatives - that carry at least one citation marker or link.
Why does a missing reference number matter so much?
A marker like [5] with no fifth reference cannot be followed, and in AI-written text it is a common sign of a fabricated citation: the model continues the numbering pattern without a source behind it. It is reported as an error for that reason.
Which citation formats are recognised?
Numbered markers such as [1], [2, 3] and [4-6], footnote markers such as [^note], Markdown links and bare URLs. The reference list is read from a References or Sources heading, or from a trailing block of lines starting with [n].
Do I need to cite common knowledge?
Usually not - that is why some flagged sentences may not need a source. Treat the uncited list as a prompt to decide, sentence by sentence, whether a reader would reasonably ask "says who?".
Is the text sent anywhere for checking?
No. Parsing and mapping happen in your browser, and no link in the text is fetched. That keeps drafts private and also means the tool cannot confirm that any link works.
Last reviewed by the A2Z.Tools team against the sources listed above.
