Claude Citation Change Log: 463 of the Top 500 Domains, a Panel the Six-Source Cap Barely Touched

This log is a dated record of what Claude cites and what changes, read from the Machine Relations Index and AuthorityTech's own daily panel. Entry one: Claude reaches 463 of the 500 most-cited domains in AI answers and cites the single most-cited source in 72 of the 93 published question segments. Claude's own counts are exact; three of the other five arms are not, so this entry reports Claude's position rather than ranking it — see the corrections of September 26 and September 25, 2026 below. The panel that tracks it day to day is the interesting story here for the opposite reason than it was for Gemini and Perplexity: Claude returns a mean of only 4.8 source URLs per answer, so the panel's six-item cap barely touched it. That is disclosed here, with the number that shows exactly how little, before this log uses the panel for anything.

Every entry states the measurement, the release or window it came from, the primary source, and what a publisher can check. Entries are appended; nothing is rewritten. Entry one draws on the Machine Relations Index, which observes six engines — Perplexity, ChatGPT, Claude, Gemini, Google AI Mode and Google AI Overviews — against a fixed basket of buying and research questions and publishes a machine-readable release daily. Entry one also covers the same methodological finding this log's ChatGPT, Perplexity and Gemini entries carry about AuthorityTech's own daily panel — the panel's citation log keeps only the first six sources per answer — but for Claude the finding runs the other direction: Claude is one of the two engines the cap barely bites.

Correction, September 26, 2026 — Gemini is a third gapped arm

The September 25 correction below named two engines with dated collection gaps. There are three. Gemini has 22 blind days inside the scoring window — May 11 to 15, then scattered single days from August 11 to September 16 — carrying 442 eligible successful runs that produced no citations. The shape is why nine sweeps walked past it: intermittent single days rather than a continuous outage, so anyone hunting an outage found none. ChatGPT, Claude and Perplexity are the arms that collected without a gap. One Claude date was flagged by the same scan and carries exactly one answer run against it, which is a scan artifact rather than a collection gap; Claude counts on this page are exact. Every Gemini count on this page is therefore a floor, and every ranking that places another engine above Gemini is withdrawn on the same logic the September 25 correction applies to the two Google surfaces: a floor can rise past a fixed count, so it settles nothing. Rankings that place an engine below Gemini still hold, because that distance can only widen.

Correction, September 25, 2026

Every ranking on this page that places an engine above Google AI Mode or Google AI Overviews is withdrawn and restated over ChatGPT, Claude, Gemini and Perplexity, of which ChatGPT, Claude and Perplexity collected without a gap and Gemini did not. The Index's own collection recorded zero citations from Google AI Overviews on any monitored query between August 15 and September 24, 2026 — 41 of the last 132 days — and zero from Google AI Mode between September 14 and September 24. The cause was a defect in the Index's Google collection path, fixed September 25, 2026: the prior collector graded a response as a success whether or not it carried content.

The direction is the whole of this correction. A presence count and a distinct-domain count only accumulate, so missing collection days can remove entries from a Google surface's count but never add them. Every Google AI Mode and Google AI Overviews figure on this page is therefore a floor: the true count is at least that and may be higher. So a claim that another engine sits below a Google surface still holds, because the gap can only widen that distance — while a claim that another engine sits above one does not, because the floor can rise past it. (This sentence, as published on September 25, read "Rankings among ChatGPT, Claude, Gemini and Perplexity are unaffected; all four collected continuously through this window." It is false — Gemini was not one of the continuously collected arms — and it is superseded by the September 26 note at the top of this page.)

Entry 1 — September 22, 2026: the baseline

Release mri_score_v2.0, contract machine_relations_index_public_view_v2.0, generated September 22, 2026. Window May 10 to September 22, 129 days, 16,307 observed answer runs, 34,720 cited-domain observations, 22,828 cited domains. A subject category paired with a question type forms a stratum, and a stratum publishes a rate only after clearing an evidence floor of 10 observed runs across 7 distinct dates; 93 of the 151 measurable strata are published today.

The Index records, for each domain, which engines cited it at least once in the window. It does not publish a per-engine citation rate, so everything below is presence and counts, not per-engine rates — the same boundary this log's companion ChatGPT, Perplexity and Gemini entries run under.

Head overlap: 463 of the top 500, exactly measured

Engine	Top 25	Top 100	Top 250	Top 500
Perplexity	25	96	244	490
Claude	23	94	237	463
Gemini	23	89	227	452
Google AI Mode	24	91	227	444
Google AI Overviews	24	89	203	378
ChatGPT	22	88	203	361

Claude misses 37 of the top 500 most-cited domains in the market, and that figure is exact. Perplexity, the other exactly measured arm, misses 10; ChatGPT, also exact, misses 139. The recorded misses for Gemini (48), Google AI Mode (56) and Google AI Overviews (122) are ceilings rather than measurements, so this entry does not place Claude above any of those three at any band — including the top-100 and top-250 bands where the recorded figures would have flattered it. Read against the domain-count section below, Claude's pattern is the inverse of Perplexity's: fewer distinct domains cited overall, but a higher share of what it does cite sits in the head the market already concentrates on.

Fifth on segment leaders

For each of the 93 published strata, take the domain with the highest citation rate in that stratum — the source the engines cite most when buyers ask that category's question — then ask which engines cite that domain anywhere in the window.

Engine	Cites the leading source, of 93 segments
Perplexity	93
Gemini	86
Google AI Mode	81
Google AI Overviews	79
Claude	72
ChatGPT	66

Claude misses the segment leader in 21 of 93 published categories — ahead of only ChatGPT. This is the one composition measure where Claude's strong head-overlap numbers do not carry through: reaching deep into the top 500 overall is not the same as reaching the single most-cited domain inside a specific category, and on that narrower test Claude sits closer to the bottom of the field than the top.

Domain count, stated without an exclusivity claim

Claude cites 5,326 of the 22,828 domains observed in the window — fewer than Perplexity, Gemini and Google AI Mode, and more than ChatGPT's 5,054. The Index recorded 2,279 for Google AI Overviews; that is a floor, so Claude is not ranked above it. This log's ChatGPT and Perplexity entries each carry a floor-adjusted exclusive-domain count for their own engine, computed against the specific release each entry used; the Gemini entry withheld one for the same reason this entry does. A floor-adjusted exclusive-share figure has to be computed against this same September 22 release to be comparable to the numbers above, and that computation has not been done for Claude. This entry states domain count and stops there, rather than publish an unconditioned exclusive-share number that this log's ChatGPT entry already had to correct once — most of an unconditioned count's weight sits on domains cited a single time.

Community platforms: below Gemini, and third of the three continuously collected engines

Twenty-seven classified domains in the Index are community and social platforms — a small set where engines diverge most.

Engine	Community platforms cited (of 27)
Google AI Mode	20
Perplexity	18
Gemini	15
Claude	10
Google AI Overviews	10
ChatGPT	8

Claude cites 10 of the 27 community platforms — ahead of only ChatGPT among the three continuously collected engines, and well behind Perplexity. It also sits below Gemini and below Google AI Mode, and those two comparisons hold in that direction precisely because both are floors: a lower bound above Claude's exact count can only move further above it. The Index recorded 10 for Google AI Overviews too, but that is a floor, so this entry does not report a tie. Combined with the segment-leader table above, Claude's composition profile is uneven rather than uniformly strong or weak: it reaches deep into the head of the index by raw domain rank, but underperforms on the two measures — segment leadership and community-platform reach — that track breadth into specific categories rather than overall citation frequency.

Three named crawlers where Gemini has none, and Perplexity has two

Unlike Gemini, which has no dedicated fetch-time citation crawler and governs training and grounding through a single log-invisible Google-Extended token, Claude is the most granular of the four engines this log has covered so far. Anthropic's own crawler documentation, last updated April 7, 2026, names three separate, log-visible user agents, each controllable independently in robots.txt: ClaudeBot, which "collect[s] web content that could potentially contribute to their training"; Claude-User, which "supports Claude AI users" by fetching a page when someone asks Claude a direct question about it; and Claude-SearchBot, which "navigates the web to improve search result quality for users" — the crawler that builds the index behind citations. Disabling Claude-SearchBot "prevents our system from indexing your content for search optimization, which may reduce your site's visibility and accuracy in user search results"; disabling Claude-User blocks retrieval of a specific page a user asked about. A publisher can, in principle, opt out of training while remaining fully citable — block ClaudeBot, allow the other two — a policy this log's Perplexity entry showed is also available there, where PerplexityBot and Perplexity-User split the same way, but which Gemini's single combined token does not permit.

This is a structural comparison, not a measurement of any specific domain's robots.txt policy — that check, run at this scale, is future work for this log, not this entry. What entry one can state is the shape of the choice available to a publisher: Claude and Perplexity each expose two or three named tokens with distinct purposes; Gemini exposes one that folds training and grounding together; and the measurement below, on how much of each engine's answer the daily panel actually saw, is unrelated to any of these robots.txt policies — it is a property of the panel's own storage, not of what a publisher blocks.

What the daily panel was actually recording

AuthorityTech runs its own tracked panel alongside the Index: 35 fixed queries, five retrieval surfaces, once a day, the same instrument behind this log's ChatGPT, Perplexity and Gemini entries and the site's 89-day per-engine churn measurement. That page documents that the daily log stores the first six sources returned by each engine, a cap that affects engines unequally. Claude is one of the two engines it barely touches.

Measured against the stored per-run answer artifacts, which preserve each provider's complete returned source list — available from September 1, 2026 onward, not for the full panel history — Claude returns a mean of 4.8 source URLs resolving to 4.1 distinct domains per answer. The daily log's six-item cap exceeded that most of the time: Claude's answers went past six sources on only 41 of 263 runs in that window — 15.6% truncated — against Perplexity's 350 of 350 (100%), Gemini's 175 of 193 (90.7%), ChatGPT's 12%, and Google AI Mode's 0%. Of the four engines whose complete-list domain counts this log has now reported, Claude's 4.1 is the lowest, and its truncation rate is the second-lowest of the five surfaces the panel tracks.

The practical consequence, recomputed rather than assumed small: day-over-day domain churn on Claude's complete source lists for the September 1–22 window (453 day pairs) is 34.2%, against 34.7% on the panel's six-source cap — a difference of 0.5 percentage points, the smallest of the four engines with a usable September sample, in the direction the six-slot depth predicts, with the cross-engine churn ranking unchanged. The full recomputation table lives on the churn page linked above; this log will not restate the panel's older 89-day retention, drop-out, and core-domain figures as if they described the complete list, because the complete-list artifacts do not reach back past September 1 and the churn page says so explicitly. Any figure in this log drawn from the panel is labelled by which list produced it.

Where other measurements land, and why they stay off this log

Third-party trackers publish their own Claude citation-depth numbers, on their own prompt baskets, and they do not agree with each other or with this log's 4.8. Orbit Media's study of 13,184 citations across four engines reports Claude averaging 3.6 sources per answer, the lowest of the four it tracked, with brands mentioned in 70% of Claude's answers but cited in only 40% — a 30-point gap. A separate tracker cited by QuickSEO puts Claude at 5.67 citations per answer, attributing Claude's retrieval to a Brave Search backend. Ahrefs data reported via GEOxylia describes Claude as citing "rarely" with "the longest citation tail of any major engine," noting only 36% of Claude's journalism citations come from the past 12 months, against a faster-turning ChatGPT citation set. None of these figures is stated here as a benchmark for this log's own number; each comes from a different query basket, a different capture method, and in most cases an unstated measurement window.

This log's 4.8 comes from a fixed panel of 35 buying and research queries measured daily since September 1, checked against the complete per-run artifact rather than a display-layer or third-party scrape. It is the lowest source-depth figure this log has reported for any of the four engines covered so far — Perplexity's 20.8, Gemini's 10.8, and Claude's own 4.8 span more than a fourfold range on the same instrument — and it is stated as what it is, not as an industry consensus figure, because the four third-party numbers above do not converge on one.

Entry 2 — September 30, 2026: head overlap holds, ChatGPT passes Claude on raw domain count

Release mri_score_v2.0, contract machine_relations_index_public_view_v2.0, generated September 30, 2026. Window May 10 to September 30, 137 observed days (up from 129 at entry one), 18,935 observed answer runs on published strata, 39,521 cited-domain observations, 25,624 cited domains (up from 16,307 runs, 34,720 observations and 22,828 domains). Published strata rose from 93 to 100 as seven thinner categories cleared the evidence floor. The same rule from the September 25–26 corrections above still governs this entry: Perplexity, Claude and ChatGPT are the three continuously collected arms; Gemini, Google AI Mode and Google AI Overviews carry floors from the dated collection gaps named above, so nothing here places Claude above any of those three, and a placement below one still holds, because a floor can only rise.

Head overlap: 465 of the top 500, up two

Engine	Top 25	Top 100	Top 250	Top 500
Perplexity	25	97	245	493
Claude	23	93	236	465
Gemini	23	88	226	451
Google AI Mode	24	92	225	444
Google AI Overviews	24	92	206	379
ChatGPT	22	87	210	377

Claude now misses 35 of the top 500 (was 37); Perplexity misses 7 (was 10); ChatGPT, the other exactly measured arm, misses 123 (was 139). All three exact arms hold their entry-one order, so the head-overlap ranking among them is unchanged since entry one.

Segment leaders: 82 of 100, Claude passes Google AI Overviews

Engine	Cites the leading source, of 100 segments
Perplexity	100
Gemini	89
Google AI Mode	87
Claude	82
Google AI Overviews	81
ChatGPT	73

At entry one, on 93 published segments, Claude cited the leading source in 72 (77%) and sat fifth of six, behind Google AI Overviews's 79. At entry two, on 100 published segments — the set is not a matched comparison, since seven categories newly cleared the evidence floor — Claude cites the leader in 82 (82%) and sits fourth, ahead of Google AI Overviews's 81. That is the one rank change among the six engines between entries.

Community platforms: unchanged at 10 of 27

Engine	Community platforms cited (of 27)
Perplexity	20
Google AI Mode	20
Gemini	15
Claude	10
Google AI Overviews	10
ChatGPT	8

Claude's count is identical to entry one. Perplexity's rose from 18 to 20; every other engine's count is unchanged.

Domain count: ChatGPT overtakes Claude

Claude cites 5,978 of the 25,624 domains observed in the window (up from 5,326 of 22,828 at entry one). ChatGPT's count rose faster, from 5,054 to 6,131, passing Claude's — the one reversal in this entry. Perplexity (11,878), Google AI Mode (7,523) and Gemini (7,405) still cite more distinct domains than Claude; Google AI Overviews's 2,412 is a floor, so Claude is still not ranked above it. No floor-adjusted exclusive-domain share has been computed for Claude against this release, for the same reason entry one gave: most of an unconditioned count's weight sits on domains cited once.

Net for entry two: Claude's position relative to the two Google surfaces improved on segment leadership and held on head overlap; its position relative to ChatGPT reversed on raw domain count while holding on head overlap and segment leadership, where Claude still leads ChatGPT in every band measured.

Entry 3 — October 1, 2026: segment leaders rise to 86 of 100, head overlap holds exactly

Release mri_score_v2.0, contract machine_relations_index_public_view_v2.0, generated October 1, 2026. Window May 10 to October 1, 138 observed days (up from 137 at entry two), 19,441 observed answer runs on published strata, 40,357 cited-domain observations, 26,071 cited domains (up from 18,935 runs, 39,521 observations and 25,624 domains at entry two). Published strata held at 100. The same rule from the September 25–26 corrections above still governs this entry: Perplexity, Claude and ChatGPT are the three continuously collected arms, so a ranking that places one of them above Gemini, Google AI Mode or Google AI Overviews is not drawn here, and a placement below one of those three still holds, because a floor can only rise.

Head overlap: Claude's own count is unchanged

Engine	Top 25	Top 100	Top 250	Top 500
Perplexity	25	97	245	493
Claude	23	93	236	465
Gemini	23	89	225	448
Google AI Mode	24	91	224	439
Google AI Overviews	24	93	208	380
ChatGPT	22	88	210	376

Claude's figures at every band are identical to entry two: 23, 93, 236 and 465 — the only one of the six engines with no movement at all on this measure. Perplexity also holds exactly. The three gapped arms moved a few domains in each direction against the current top-500 set, which reranks every release; because each is a floor, that movement describes which domains cleared into today's top 500, not a change in any engine's true citation count, and no new ranking is drawn from it. ChatGPT, the other exactly measured arm, gained one domain at the top-100 band and lost one at the top-500 band — within the release-to-release noise this log has recorded before.

Segment leaders: 86 of 100, the real move this entry

Engine	Cites the leading source, of 100 segments
Perplexity	100
Gemini	88
Claude	86
Google AI Mode	85
Google AI Overviews	80
ChatGPT	77

Claude cites the leading source in 86 of 100 published segments, up from 82 at entry two and 72 of 93 at entry one — the largest single-release move this log has recorded for Claude on any measure. Claude's recorded count now sits numerically above Google AI Mode's 85 and Google AI Overviews's 80, but both of those are floors under the September 25–26 corrections, so neither comparison is drawn: a floor can rise past an exact count on the next release the way Google AI Overviews's own count rose past 81 at entry two. Entry two drew that comparison against Google AI Overviews; this entry does not repeat it, for the same reason the corrections above already state. What is safe to say, because it rests only on Claude's own exact count: Claude's segment-leader share has risen at every release recorded so far — 72, then 82, then 86 — while its head-overlap count has not moved since entry two.

Community platforms: unchanged at 10 of 27

Engine	Community platforms cited (of 27)
Perplexity	20
Google AI Mode	20
Gemini	15
Claude	10
Google AI Overviews	10
ChatGPT	8

No engine's count moved since entry two.

Domain count: ChatGPT's lead over Claude widens slightly

Claude cites 6,110 of the 26,071 domains observed in the window (up from 5,978 of 25,624 at entry two). ChatGPT's count also rose, from 6,131 to 6,272, holding its entry-two lead over Claude and widening the gap from 153 to 162 domains. Perplexity (12,168), Google AI Mode (7,540) and Gemini (7,449) still cite more distinct domains than Claude; Google AI Overviews's 2,455 is a floor, so Claude is still not ranked above it. No floor-adjusted exclusive-domain share has been computed for Claude against this release, for the reason entry one gave.

Net for entry three: Claude's position against Gemini and the two Google surfaces is unchanged on head overlap and not newly compared on segment leadership, for the methodological reason given above. Its position against ChatGPT, the other exactly measured arm, held on domain count (still behind, by a slightly wider margin) and on head overlap and segment leadership, where Claude still leads ChatGPT in every band and on the published-segment count. The one real movement this entry records is Claude's own segment-leader share, which has now risen at both releases since entry one.

How to read this log

Each future entry compares a release or a panel window against the one before it and reports what moved. Four numbers are the ones to watch:

• Head overlap. 237 of the top 250, 463 of the top 500.
• Segment leaders cited. 72 of 93.
• Community platforms. 10 of 27.
• Panel-recorded source depth. 4.1 distinct domains per answer on the complete list, against a six-item cap that only bit 15.6% of runs; watch for that share moving as the answer-evidence store's history lengthens past September 1.

A change in any of them is an entry. A release with none is recorded as no change.

What a publisher should take from entry one

Claude is the clearest case in this series of an engine whose overall reach understates its concentration. It cites fewer distinct domains than Perplexity, and fewer than the floors recorded for Gemini and Google AI Mode — both of those comparisons hold, because a floor above Claude's exact count can only move further above it. Yet it reaches deeper into the top 100 and top 250 of the index than ChatGPT, the only other exactly measured arm below it: a narrower, more head-weighted citation set rather than a wide one. Where it sits against the three gapped arms at the head is not something this release can settle. Where it falls down is segment leadership: missing the top-cited source in 21 of 93 categories means a brand that is not already the leading answer in its specific category cannot assume Claude's strong aggregate numbers will carry it there.

The measurement finding confirms the panel's Claude figures. A dashboard, a competitor tracker, or an internal panel that caps a citation array at six entries per answer will report close to the true count for Claude and Google AI Mode, understate ChatGPT modestly, and understate Perplexity and Gemini severely. Claude's answers exceeded the six-item cap on only 41 of 263 runs — the panel's Claude numbers sit closest to the complete artifact of any engine measured, within 0.5 percentage points on churn.

Watch list for entry 4

• Whether Claude's segment-leader share keeps rising or plateaus at the next release — it moved at both releases recorded so far (72, then 82, then 86).
• Whether a floor-adjusted exclusive-domain count for Claude gets computed against a specific release, making that comparison publishable without the caveat in entry one.
• Whether the complete per-run artifact history extends further back than September 1, letting the panel restate churn over a longer window than 22 days.
• Whether any additional top-500 domain moves into or out of Claude's cited set, or whether the 14-of-100 segment-leader gap narrows further.

Frequently asked questions

Is Claude's citation set simply smaller than the other engines', or is it different in kind? Both. Claude cites fewer distinct domains overall than Perplexity, Gemini or Google AI Mode, but a higher share of what it does cite sits inside the head of the index — the pattern of a concentrated set, not just a small one. It falls to the bottom half of the field only on segment leadership, where reaching a specific category's top-cited source matters more than overall reach.

Why does the six-source panel cap barely affect Claude when it affects Gemini and Perplexity much more? Because the cap only bites when an engine's true answer exceeds six sources, and Claude's complete-list mean is 4.8 URLs — below the cap most of the time. Claude's answers passed six sources on only 41 of 263 runs in the September 1–22 window, against 100% of Perplexity's and 90.7% of Gemini's. The cap is a property of the panel, not of the engine, and for a shallow-answering engine like Claude it simply has little to bite into.

Does Claude having three named, log-visible crawlers instead of Gemini's one make it easier to measure Claude's crawl behavior? It makes the robots.txt policy easier to read and control — a publisher can distinguish training, search indexing and live user fetches in server logs the way they cannot with Gemini's single combined token. It does not by itself change what this log can say about citation counts or churn, which come from the Index and the daily panel rather than from crawler logs; a domain-by-domain robots.txt check for Claude, in the style of this log's Perplexity entry, is future work, not something entry one attempts.