Search intelligence firm Adthena published a free weekly index of brands advertising inside ChatGPT, observing 7,378 distinct advertisers across three markets in the week of July 13 to 20, 2026, alongside a claim that ad placements on the platform grew 97 times between April and June.

The dashboard, called the ChatGPT Ads Share of Search Index, carries data for the week of July 13 to 20, 2026 and covers the United States, the United Kingdom and Australia in detail, with all remaining territories grouped into a combined rest-of-world bucket. It represents the first publicly accessible, regularly updated count of advertiser participation in a channel that did not exist six months ago.

Separately, in an email dated July 22, 2026, Adthena disclosed three figures drawn from a forthcoming quarterly report scheduled for release on Monday, July 27. According to the company, ChatGPT ad placements grew 97x from April to June 2026; ChatGPT ad frequency in the United States reached 24.7% against 5.8% for Google AI Mode; and Google AI Overview ad volume rose 278% quarter over quarter.

Those three numbers, if they hold, describe a channel that has moved from novelty to routine inventory inside a single quarter. They also sit awkwardly against Adthena's own published measurements from a month earlier, a contradiction the company has not addressed publicly.

What the index actually counts

The methodology is narrow and the company states it plainly. Each advertiser's visibility percentage equals the number of prompts on which that advertiser has been observed, divided by the total number of prompts in the dataset for the selected scope, whether a single market or all markets combined. The engine monitored is ChatGPT. The data window is the seven days from July 13 to 20, 2026.

That definition matters because it is a share-of-prompts measure rather than a share-of-impressions or share-of-spend measure. An advertiser appearing once on many prompts scores higher than an advertiser appearing many times on few prompts. The metric describes breadth of prompt coverage, not budget weight or delivered volume.

The index breaks out three markets by advertiser count. The United States accounts for 4,982 unique advertisers, or 60.1% of the total observed footprint. The United Kingdom follows with 1,342, at 16.2%. Australia contributes 912, at 11%. The combined rest-of-world category holds 1,055 advertisers, representing 12.7% of the total. Adthena notes that many advertisers run across multiple markets simultaneously, which means those figures overlap rather than sum cleanly to the 7,378 headline.

The geographic distribution tracks the platform's rollout sequence closely. The United States received ChatGPT ads first, on February 9, 2026. Australia arrived in the March expansion. The United Kingdom went live on June 6, 2026, the first European market to receive the pilot. A five-month head start producing a sixty-percent share is not surprising; what is more notable is that the UK, roughly seven weeks into activation at the time of measurement, already contributes a sixth of all observed advertisers.

Who is winning prompt coverage

Ranked across all tracked markets, Booking.com holds the top position at 13.81% visibility, appearing in Australia, the United Kingdom, the United States and the rest-of-world grouping. Almedia USA, Inc. follows at 12.76%, with the same four-market footprint. efaq.com sits third at 4.55%.

The gap between second and third place is the most striking feature of the ranking. Two advertisers hold more than 12% visibility each. The next eight are clustered between 3.47% and 4.55%. Expert Market records 4.38% across Australia, the UK and the US. giffgaff holds 4.28%, confined to the UK. Jotform reaches 4.17% across four market groupings, Variant Group LLC 4.11%, BestMoney 3.88% across the UK and US, Lovable 3.66%, and Vodafone 3.47% in the UK only.

Market-level rankings differ from the blended list. In the United States, Booking.com leads at 8.7%, followed by Almedia USA, Inc. at 8.1% and BestMoney at 6.1%. The United Kingdom shows a distinctly local pattern: giffgaff tops the market at 14.0%, Vodafone follows at 11.3%, and Booking.com places third at 9.0%. In Australia, Booking.com leads at 13.4%, Almedia USA, Inc. at 12.4%, and Finder AU at 10.9%.

Two telecommunications brands occupying the top two UK positions, neither of which appears in the top three of any other market, suggests that prompt-level competition is forming along national commercial lines rather than resolving into a single global advertiser set. It also suggests that the UK auction, whatever its absolute volume, is being contested by domestic incumbents rather than by international brands extending existing campaigns.

The category concentration is worth noting on its own terms. Travel booking, mobile telecommunications, financial comparison, form software and price comparison dominate the top ten. These are categories where the purchase decision involves comparison across a defined option set, which is structurally close to what conversational queries produce.

The prompts drawing the most competition

Adthena publishes the number of unique advertisers competing on the five most contested prompts per market, scoped so that advertisers in different countries are never counted as competing on the same prompt. In the United States, the top two prompts each attracted 23 unique advertisers, with the following three drawing 20 each.

The US prompt text is visible in the published index and clusters entirely around hospitality software and small business accounting: queries about cheapest Airbnb management software, how to choose a channel manager for hosts, best small business accounting software for 2026, best channel manager for hosts comparing Hostaway against Lodgify, and a three-way comparison between Guesty, Hostaway and Lodgify.

Four of those five are software purchase decisions in a single vertical. Two are explicit head-to-head vendor comparisons. That pattern is consistent with what the channel's targeting mechanism rewards. Targeting in ChatGPT operates through context hints, phrases advertisers supply describing the conversation types where their products may be relevant, rather than through keyword lists. A prompt naming three competing vendors is unusually legible to a context-matching system, and the concentration of 20 or more advertisers on such prompts suggests advertisers have identified that legibility.

Twenty-three advertisers competing on a single prompt is a meaningful density figure for a channel that opened to self-serve buying in the United States on May 5, 2026. It is also, at a maximum of 23, well short of the hundreds of bidders that contest competitive Google Ads auctions in the same verticals.

The 97x figure and what it can and cannot support

The quarterly growth claim carries the most weight and the least documentation. Adthena states that ChatGPT ad placements grew 97x from April to June 2026. No base figure accompanies that multiple in the material circulated ahead of the July 27 report, which means the absolute placement counts at either end of the window remain undisclosed.

That omission is consequential. A 97x increase from a small base and a 97x increase from a substantial base describe different market conditions, and the multiple alone does not distinguish between them. What is known about the April starting point suggests the base was low. ChatGPT CPMs had fallen to as low as $25 by mid-April, down from $60 at launch, a decline consistent with inventory outpacing demand. The pilot had surpassed 600 advertisers by late April, when Adthena released AdBridge, a free tool porting Google Ads campaigns into ChatGPT.

Between April and June, three structural changes occurred that would plausibly drive placement volume sharply upward. OpenAI opened self-serve buying to all US businesses on May 5, adding cost-per-click bidding and removing the minimum spend requirement entirely. The UK activation followed on June 6. Japan and South Korea went live on June 22, alongside UK self-serve access. Each of those events expanded either the buyer pool or the addressable inventory, and the compounding effect across a single quarter offers a mechanical explanation for a large multiple without requiring any assumption about advertiser enthusiasm.

The 24.7% US ad frequency figure invites a similar reading. Compared against 5.8% for Google AI Mode, the ratio is slightly over four to one. But the two surfaces are not equivalent products. AI Mode is a search interface where a substantial share of queries are informational and where Google has restricted advertising in sensitive verticals. ChatGPT serves ads only to Free and Go tier users, with Plus, Pro and Enterprise subscribers excluded entirely, which concentrates all observed ad load into a subset of the user base. Frequency measured against different denominators is not a like-for-like comparison, and neither company publishes the denominator.

A measurement contradiction that remains open

Adthena's own recent output complicates the picture. In July, the company circulated its Monthly AI Data Pulse for June 2026, which recorded a 0.00 percent ChatGPT ad frequency across 169,560 UK scrapes and zero ChatGPT ad items among 29,237 total ad items catalogued across all markets for the month. That same report contained a separate section documenting specific UK ChatGPT ad activity following the June 6 launch, an internal inconsistency the document did not resolve.

The new index describes 1,342 UK advertisers active in a single week in July. The June report described an empty UK market across nearly 170,000 observations. Both figures originate from the same company.

Timing may reconcile part of the gap. UK self-serve access arrived on June 22, eight days before the June monitoring window closed, and a market that opened to unrestricted buying at the end of a measurement period would register little activity within it. The index measures a week in mid-July, three weeks later. Yet the June report claimed zero ChatGPT ad items across all markets, including the United States, where the channel had been active since February and where the same company now reports 4,982 advertisers. A methodology change between the two datasets is the most plausible explanation, but Adthena has not published one.

The 278% quarter-over-quarter increase in Google AI Overview ad volume sits against a similar backdrop. Adthena first detected ads inside AI Overviews on November 24, 2025, finding 13 instances across 25,000 monitored results pages, a frequency of 0.052%. The June Data Pulse put US AI Overview ad penetration at 0.16 percent, meaning roughly 16 in every 10,000 AI Overviews carried a paid placement. A 278% quarterly increase applied to a base measured in hundredths of a percentage point produces a figure that remains small in absolute terms.

Why this matters for marketers

The index is the first free, recurring public count of who is advertising inside ChatGPT, and that scarcity is the point. Independent verification of activity in the channel has been minimal since it launched. Most circulating figures come from parties with a commercial position in the outcome. Criteo reported more than 1,000 brands live through its API connection, drawn from its own client base. Similarweb data cited in May put the overall ChatGPT click-through rate at 0.68 percent. Adthena's numbers are Adthena's, produced by a company selling ChatGPT competitive intelligence and using the free index as the entry point to a paid product.

That commercial context does not make the data wrong. It does mean no audited third-party standard exists against which to check it, and the discrepancy between the June and July datasets illustrates precisely why one would be useful.

For advertisers assessing whether to enter, the prompt-level concentration data is arguably more informative than the headline counts. A maximum of 23 unique advertisers competing on the most contested US prompt describes an auction that is populated but not saturated. The vertical clustering visible in those prompts, heavily weighted toward software comparison and hospitality tools, suggests early adoption has been concentrated among advertisers whose products map cleanly onto comparison-shaped questions.

Ad penetration in ChatGPT reached 26% of US desktop chats in June 2026, according to Similarweb, up from 14% in May. That independent figure sits close to Adthena's 24.7% frequency claim, and the rough agreement between two unrelated methodologies is one of the few points of external corroboration currently available for any ChatGPT advertising statistic.

The channel remains young enough that its measurement infrastructure is being built in public, by vendors, while the auction it measures is still forming. Adthena's own record over eight months, from detecting 13 ads across 25,000 AI Overview pages in November to counting 7,378 ChatGPT advertisers in a single July week, is a reasonable proxy for how quickly the underlying surface has changed. Whether the measurement has kept pace is a separate question, and the gap between the June and July numbers is where it currently sits unanswered.

Timeline

Summary

Who: Adthena, a London-founded search intelligence company established in 2012, which sells competitive visibility tools for Google paid search and ChatGPT advertising. The advertisers named in the index include Booking.com, Almedia USA, Inc., efaq.com, Expert Market, giffgaff, Jotform, Variant Group LLC, BestMoney, Lovable, Vodafone and Finder AU.

What: A free weekly public dashboard called the ChatGPT Ads Share of Search Index, observing 7,378 distinct advertisers across three detailed markets, alongside three figures circulated ahead of a quarterly report: 97x growth in ChatGPT ad placements from April to June 2026, US ChatGPT ad frequency of 24.7% against 5.8% for Google AI Mode, and a 278% quarter-over-quarter rise in Google AI Overview ad volume.

When: The index covers the week of July 13 to 20, 2026. The supporting figures were circulated on July 22, 2026, ahead of a full quarterly report scheduled for July 27, 2026.

Where: The index breaks out the United States, with 4,982 advertisers and a 60.1% share; the United Kingdom, with 1,342 advertisers at 16.2%; and Australia, with 912 advertisers at 11%. A combined rest-of-world grouping accounts for 1,055 advertisers, or 12.7%.

Why: No audited third-party measurement standard exists for ChatGPT advertising, and most published participation figures originate from companies with a commercial interest in the channel. The index provides a recurring public count, though its July figures stand in unexplained contrast to the same company's June measurement, which recorded zero ChatGPT ad items across all markets.