What Sources Does ChatGPT Use? Reddit's Share of AI Citations, Measured (2026)

What sources does ChatGPT use? Mostly Wikipedia, brand and vendor sites, review publishers and official documentation, and in 2026 much less Reddit than the GEO playbooks assume. Reddit's share of ChatGPT Search citations fell from 3.83% to 0.52% in four days in August 2026, while Google's AI surfaces barely moved and Perplexity still leans on Reddit more than any other site.

TL;DR: In Profound's 680 million citations, Reddit was 11.3% of ChatGPT's top-10 sources against 46.7% on Perplexity and 21.0% on Google AI Overviews. Promptwatch then measured Reddit falling from 3.83% to 0.52% of ChatGPT Search citations between early and mid-August 2026. In our own test on 7 November 2026, 2 of 20 everyday ChatGPT answers linked reddit.com, and 5 of 61 links went there.

This is an independent data study from redditapis.com, a third-party Reddit API that is not affiliated with Reddit, Inc. It pulls the public numbers on where ChatGPT's answers come from into one place, adds a small test of our own, and says what each number can and cannot tell you. What Reddit data is still worth mining after the drop is covered in our market research analysis; how Reddit's paid data access works is in the Reddit Data API overview.

What sources does ChatGPT use to answer questions?

ChatGPT uses two kinds of source: the text it was trained on, which it cannot link to, and live web pages it fetches when it searches, which it can cite. Every citation number in this post measures the second kind, the links ChatGPT Search shows under or inside an answer, not what shaped the model during training.

OpenAI's help centre says its models are developed from three primary sources: publicly available information on the internet, information accessed through third-party partnerships, and information that users, trainers or researchers provide. The live search side is where measurement is possible, and it is what GEO teams track. The sources that show up there, by the large public studies:

• Encyclopedic reference. Wikipedia is ChatGPT's single most cited domain in Profound's data, at 7.8% of all citations.
• Vendor and brand sites. Pricing pages, product pages and help centres, which ChatGPT now searches directly with site: queries.
• Review and editorial publishers. Forbes, TechRadar, RTINGS and similar, which carry comparisons.
• Software review platforms. G2 shows up at 1.1% of ChatGPT's citations in Profound's sample.
• Community and forum content. Reddit was the second most cited domain in that sample at 1.8%, before the August 2026 drop.

The training side is a separate question. OpenAI and Reddit announced a partnership in May 2024 that gave OpenAI access to Reddit's Data API, so Reddit text informs the model whether or not a given answer links to it. Our AI training data guide covers that side.

How much does ChatGPT cite Reddit compared with other AI engines?

Much less than the others. In Profound's study of 680 million citations from August 2024 to June 2025, Reddit was 11.3% of ChatGPT's ten most cited sources, against 21.0% for Google AI Overviews and 46.7% for Perplexity. On ChatGPT, Wikipedia took 47.9% of the top ten.

Reddit's rank in each engine's top-10 list, from that study:

• Perplexity: Reddit at 46.7%, the most cited source.
• Google AI Overviews: Reddit at 21.0%, the most cited source.
• ChatGPT: Reddit at 11.3%, behind Wikipedia at 47.9%.

The full picture, from Profound's AI Platform Citation Patterns study:

Two denominators matter here. The top-10 share asks how much of an engine's favourite-source list is Reddit. The overall share asks how much of every citation is Reddit. ChatGPT spreads its citations across many more domains, so Reddit can be its second most cited site and still only 1.8% of the total.

Profound's sample is the largest public one, covering ten months of answers across three engines before the August 2026 change, and these are the four numbers worth remembering from it:

What happened to Reddit's ChatGPT citations in August 2026?

Reddit's share of ChatGPT Search citations averaged 3.83% from 18 July to 7 August 2026, then 0.52% from 14 to 17 August, an 86.4% relative drop measured by Promptwatch. The slide started on 8 August and the steep fall came on 14 August. Google's AI surfaces moved far less over the same window.

Promptwatch first published the data on 18 August, and its co-founder's post on X carried it to over 2.7 million views:

Klaas

@forgebitz

looks like reddit is almost wiped from chatgpt sources the query fanout changes had a big impact and the past couple of days it seems to be almost completely removed from prompt responses https://t.co/oCGm9M0yPO https://t.co/c2GJF2apG7

The numbers, from Promptwatch's 20 August analysis:

The story reached the front of r/technology through the Axios write-up, and founders on r/SaaS picked it apart the same week:

r/

r/SaaS·u/ProjectBacklink

GEO Update: ChatGPT has stopped citing reddit

Promptwatch published some interesting data on a fairly sudden change in ChatGPT Search. The main numbers: -From July 18 to August 7, Reddit accounted for an average of 3.83% of ChatGPT Search citations. -From August…

2814

Open on Reddit

The sharpest reply under it read the site: number, not the Reddit number:

Why did ChatGPT stop citing Reddit?

OpenAI has not said. The best-supported explanation is a change to how ChatGPT Search writes its background queries on 8 August 2026: Promptwatch saw queries using the site: operator jump from about 0.37% to 16.8% of all fan-out queries in a single day, so ChatGPT began asking official domains directly instead of searching the open web.

Promptwatch also saw ChatGPT run more searches per answer, from about 1.08 to 1.83. A search scoped to a brand's own site cannot return a Reddit thread, which fits a drop in Reddit citations that started the same day.

The explanations people have offered, and what supports each:

• site: targeting. Measured by Promptwatch, and it lines up with the date of the first slip.
• Licensing talks. Reported in commentary, unconfirmed; Reddit's deals with OpenAI and Google run through its Data API.
• Spam and quality filtering. Plausible after a year of brands seeding threads for AI visibility, unconfirmed.
• A measurement artifact. Promptwatch itself says a collection issue cannot be ruled out yet.
• Read but not cited. A tracker reported ChatGPT still reads Reddit threads while showing fewer links.

None of these is confirmed, and they are not exclusive: a licensing dispute and a quality filter would both show up as fewer Reddit links.

How does ChatGPT Search decide which sources to show?

ChatGPT Search turns one prompt into several sub-queries, runs them, reads the pages that come back, and shows a subset of those pages as citations. The visible links are the end of that funnel, not the whole of it, so a source can inform an answer without ever appearing as a link.

The pipeline, as the trackers describe it from the outside:

• Prompt. You ask a question in plain language.
• Fan-out. ChatGPT writes several search queries, often adding words like best, reviews or the current year.
• Search. The queries run; since 8 August 2026, a sixth of them are scoped with site: to a named domain.
• Read. ChatGPT fetches pages, threads and documentation from the results.
• Cite. A subset of what it read becomes the links you see.

That last step is why several practitioners argue ChatGPT may still read Reddit while showing it less. No tracker can see what ChatGPT read and did not cite, so treat that as a hypothesis. A September r/SaaS thread compared engines on the same prompts instead:

What did our own ChatGPT test find in November 2026?

Reddit was nearly absent. We sent 20 everyday prompts to ChatGPT's public web app on 7 November 2026 and counted every link in the answers. The 20 answers carried 61 links; 5 went to reddit.com, and they sat in only 2 answers. Six answers had no links at all.

What stood out in the answers:

• Shopping prompts linked retailers and brands. The espresso answer linked four Target product pages; the keyboard answer linked Walmart, Best Buy and two brand stores.
• Software prompts linked vendor pricing pages. All five CRM links were the vendors' own sites, the pattern the site: change predicts.
• Reviews of a developer tool linked Reddit. The one prompt asking for honest user reviews of Cursor linked four Reddit threads, plus Product Hunt and a sentiment analysis page.
• Reddit appeared as a word more than a link. The Framework laptop answer cited "a recent Reddit discussion" in the text without linking it.
• One reddit.com link was a homepage. The first-100-users answer linked reddit.com as a channel to post in, not as a source.

Link counts tracked the type of question. Buying questions drew the most links, all of them to sellers and reviewers:

By type of site rather than type of question, the 61 links split as follows, with sellers and their own help pages well ahead of any community:

A 20-prompt sample cannot measure a percentage to a decimal place, and we did not try. It shows the shape: for buying and how-to questions, ChatGPT now points at the people who sell or document the thing. A separate r/aeo test posted on 29 October 2026 reported the same pattern from a different angle, with 0 of 49 shopping answers citing Reddit.

Which sites does ChatGPT cite instead of Reddit now?

Official and commercial domains. In our test, 42.6% of links went to vendor and brand sites, 13.1% to documentation, 13.1% to review publishers and 9.8% to retailers. Community platforms, Reddit included, were 14.8%, and most of that came from a single review question.

Grouped by what the site is:

This matches what Promptwatch inferred from the fan-out data: ChatGPT now asks the official site first. For a GEO team, the practical read is that your own pricing and spec pages, in plain HTML, matter more for ChatGPT than a seeded thread does.

Does Google AI Overviews still cite Reddit in 2026?

Yes, close to its old rate. Promptwatch measured Reddit at about 2.37% of Google AI Overviews citations in early July 2026 and 2.10% in mid-August, an 11.3% relative decline with no cliff. In Profound's larger dataset Reddit was the single most cited source in AI Overviews, at 21.0% of its top ten.

Practitioners running the same prompts across engines see the same split. One September comparison on r/SaaS:

Google has a direct line to Reddit's content: Reddit expanded its partnership with Google in February 2024, giving Google structured access through the Data API. What that means for a team choosing where to measure:

• Google AI Overviews: Reddit is still a top source; track it there.
• Google AI Mode: Reddit fell 30.5% in the same window, a real but partial decline.
• ChatGPT Search: Reddit is now a minor source for most question types.
• Perplexity: Reddit led its top-10 sources at 46.7% in Profound's data; no August 2026 figure was published.

Edward Sturm's video on the drop covers what SEO teams can do next:

Reddit Citations Just Collapsed in ChatGPT. What SEOs Do Next

Edward Sturm

Has Reddit's share of ChatGPT citations collapsed before?

Yes, a year earlier. Semrush's 230,000-prompt study found ChatGPT's Reddit citations fell from about 60% of responses in early August 2025 to roughly 10% by mid-September 2025, a drop Kevin Indig tied to Google removing its num=100 search parameter. Reddit then recovered: Profound found its citation share nearly doubled from October 2025 to January 2026.

The sequence, from both deals to the latest test:

• February 2024. Reddit expands its Google partnership through the Data API.
• May 2024. Reddit and OpenAI announce a partnership with Data API access.
• August to September 2025. ChatGPT's Reddit citations fall from about 60% to 10% of responses, per Semrush.
• October 2025 to January 2026. Reddit's citation share nearly doubles, per Profound's trend report.
• 8 August 2026. ChatGPT's fan-out starts using site: at scale.
• 14 August 2026. Reddit falls to 0.52% of ChatGPT Search citations.
• 7 November 2026. Our test: 2 of 20 answers link reddit.com.

Two collapses in twelve months, one followed by a recovery, is the strongest argument against treating either number as permanent.

How did people react to the drop on Reddit and X?

The reaction to the drop peaked in August 2026 and has not stopped. We searched Reddit through our own API on 7 November 2026 for the most relevant posts of the past year about ChatGPT and Reddit citations: 23 of the 35 posts returned, 66%, were written on or after 14 August 2026, and 14 of the 35 in August alone.

The pull itself is one request:

curl -sS "https://api.redditapis.com/api/reddit/search?q=chatgpt%20reddit%20citations&sort=relevance&t=year&limit=100" \
  -H "Authorization: Bearer $REDDITAPIS_KEY"

On X, the takes split between "Reddit is over for GEO" and "it will come back". One widely shared thread argued the bigger change was how ChatGPT searches, not Reddit itself:

Jake Ward

@jakezward

Reddit is disappearing from ChatGPT citations right now, but I honestly think everyone is focusing on the wrong part of the story: Reddit isn't what matters most here. Because something much bigger seems to have changed in how ChatGPT searches. 8 August: ChatGPT started citing… Show more

What the reactions had in common:

• Practitioners asked for patience. Several pointed to Promptwatch's own provisional caveat.
• GEO agencies split. Some saw a loophole closing; others reported no change for their clients.
• Regular users cheered. The r/technology top comments welcomed fewer Reddit links in answers.
• Analysts asked for per-topic data. Nobody has published which topics lost Reddit citations and which kept them.

Searching comments and threads like this by topic is covered in our Reddit search API tutorial and the comment search guide.

Does Reddit still matter for AI search in 2026?

Yes, but not as a ChatGPT citation lever. Reddit is still a top source in Google AI Overviews and Perplexity, still ranks in Google's organic results, still feeds model training through licensed data, and may still be read by ChatGPT even when it is not linked. What changed is that a thread is no longer a reliable way into ChatGPT Search's visible sources.

Where Reddit still earns its place:

• Google AI Overviews and Perplexity. Reddit leads both in the largest public dataset.
• Training data. The OpenAI and Google deals license Reddit content through the Data API; see our licensing explainer.
• Demand research. Threads show what buyers ask and complain about, which no citation share measures; our sentiment analysis guide shows how to read it.
• Retrieval for your own agents. A RAG pipeline or agent can read Reddit directly instead of waiting for an engine to cite it; see the Reddit RAG data source guide and Reddit API for AI agents.

What should GEO and SEO teams do about ChatGPT sources now?

Measure each engine separately, fix the pages ChatGPT now searches first, and read Reddit directly instead of relying on a citation to tell you it mattered. A single AI visibility number that blends ChatGPT, Google and Perplexity will hide exactly the change that happened in August 2026.

A checklist for this quarter:

• Measure per engine. ChatGPT, AI Overviews, AI Mode and Perplexity moved by very different amounts.
• Name the surface. One tracker on X found the ChatGPT app and the OpenAI API picking sources differently in the same week.
• Fix your own pages. Put pricing, specs and the actual answer in plain HTML so a site: look-up finds them.
• Keep Reddit for people. Threads still rank on Google and still get read by buyers.
• Read Reddit directly. Pull the threads your buyers write with the Reddit search API or set a Reddit monitor for your brand terms.
• Re-test monthly. The share moved twice in twelve months; a quarterly check is too slow.

For a live watch on brand mentions rather than a monthly pull, our guide to how Reddit monitoring works covers the setup, and the MCP server puts the same search inside Claude or Cursor.

How we gathered these numbers: methodology

This study combines three sources, each with its own limits. Published third-party datasets give the scale, Promptwatch gives the timing of the August 2026 change, and our own two small pulls show what the pattern looks like in practice on one day. No number here comes from OpenAI.

What each source is and is not:

• Profound, 680 million citations, August 2024 to June 2025. The largest public sample; it predates the August 2026 drop.
• Promptwatch, daily ChatGPT Search share, July to August 2026. Real-interface monitoring; no sample size published, and the company calls the drop provisional.
• Semrush, 230,000 prompts, August to September 2025. The source for the earlier collapse.
• Our ChatGPT test, 20 prompts, 7 November 2026. One fresh chat per prompt in ChatGPT's public web app; every linked URL counted; a pilot prompt about Reddit itself excluded.
• Our Reddit search, 35 posts, 7 November 2026. One relevance-sorted search over the past year through our API, with each post's created date read from the response.

Pricing for the Reddit pulls is on the pricing page, and the first 1,000 reads each month are free.