Which AI detectors were shut down? Every withdrawal on the record, with the vendor's own statement
Three AI detectors on the index record had been withdrawn or paused by their makers when this page was written, by the vendor pages and archived captures read on 9 November 2026, and three more joined the table on 10 November 2026 with the eleventh wave of cards, AI Writing Check (the vendor's August 2023 notice), Grammica (removed in the January 2026 site relaunch) and GPT Radar (a redirect to neuraltext.com since 14 August 2026), each dated below from its own page or the Wayback Machine index (AI Writing Check card, Grammica card, GPT Radar card, read 10 November 2026). The first three: OpenAI's AI Text Classifier, withdrawn on 20 July 2023 "due to its low rate of accuracy" (openai.com, read 8 November 2026); Writer's AI Content Detector, sunset on 22 December 2025 together with its API endpoint (archived writer.com page, captured 9 December 2025, read 9 November 2026); and the hosted demo of OpenAI's 2019 GPT-2 Output Detector, paused on Hugging Face while the code and weights stay public (openai-openai-detector.hf.space, read 9 November 2026). Between them the three tools appear in 10 of the 35 study records in the index, so a reader who meets a 2023 result will often meet a tool that no longer runs. Four more withdrawals joined the table on 10 November 2026 with the tenth wave of cards, each with the vendor's own notice or the archive record where no notice exists: Wordtune's AI Content Detector, whose page has returned 404 since the Wayback capture of 26 July 2025 with no statement (Wordtune card); Check For AI, sunset by a banner of June 2023 and a notice from 23 July 2023 (Check For AI card); Writefull's GPT Detector, discontinued by 7 March 2025 because, in the vendor's words, detection tools "have high error rates" (Writefull card); and Passed.ai, closing with its team joining Originality.ai (Passed.ai card), all read 10 November 2026. A fourth withdrawal, of one feature rather than a whole tool, joined the table on 9 November 2026: Copyleaks removed AI detection for source code from its API, per release notes dated 28 August 2025 and 16 December 2025 (docs.copyleaks.com, read 9 November 2026).
The table lists every withdrawal the index can source to a vendor statement or a dated capture. A tool enters the table only when its maker said it was withdrawn, paused or sunset, or when an archived page shows the announcement; a tool that merely went quiet, changed its name or was absorbed into another product is not listed, because the index records what was published and not what it infers. This page is one of the questions answered from the index; its siblings ask how many AI detectors exist and which detectors share an owner, and every AI detector card sits in the detectors hub.
| Tool | Withdrawal date | Vendor statement, as published | Source | Read date |
|---|---|---|---|---|
| OpenAI AI Text Classifier (record) | 20 July 2023 (released 31 January 2023) | "As of July 20, 2023, the AI classifier is no longer available due to its low rate of accuracy" | openai.com | 8 November 2026 |
| Writer AI Content Detector (Writer card) | 22 December 2025 | "Important update: This tool will be sunset on December 22 along with the AI detection API endpoint"; the page has redirected to writer.com since 24 December 2025 | web.archive.org capture of writer.com | 9 November 2026 |
| Writer AI detection API, POST /v1/tools/ai-detect (the same card) | 22 December 2025 | The endpoint "is deprecated and will be removed on December 22, 2025"; the legacy enterprise endpoint is marked deprecated in the live reference | archived dev.writer.com page; legacy API reference | 9 November 2026 |
| GPT-2 Output Detector hosted demo (GPT-2 Output Detector card) | Paused at the read date; no pause date published | The Hugging Face Space shows a paused state; the GitHub repository is archived with a last commit of 13 December 2023; code and weights remain under the MIT License | openai-openai-detector.hf.space; github.com/openai/gpt-2-output-dataset | 9 November 2026 |
| DetectGPT hosted demo (DetectGPT card) | Gone by 26 November 2023; no statement published | detectgpt.ericmitchell.ai returned 404 on 9 November 2026; the Wayback Machine index shows a last 200 capture on 20 August 2023 and a 404 from 26 November 2023; the MIT-licensed code remains on GitHub | github.com/eric-mitchell/detect-gpt | 9 November 2026 |
| BrandWell AI Content Detector page (BrandWell card) | Redirecting since 29 August 2026; not shut down | The detector page 301s to the AI Content Detector Mod on the Moxby marketplace, per the Wayback CDX record; the detector is sold on as a Mod and inside the WriteWell app, so this is a move, not a withdrawal | brandwell.ai/ai-content-detector; moxby.com | 9 November 2026 |
| Copyleaks AI source code detection, API (Codeleaks card) | 28 August 2025 (standalone endpoint deprecated) and 16 December 2025 (verdict removed from the submit endpoints) | Release notes: the standalone source-code endpoint POST api.copyleaks.com/v2/writer-detector/source-code/{scanId}/check deprecated on 28 August 2025; on 16 December 2025 "the properties.aiGeneratedText feature will no longer support source code files", with "This change only affects AI detection for programming languages and source code. AI Content Detection for natural language text continues to be fully supported."; the Codeleaks marketing page keeps "AI Code Detection" in its title and sells code licence and plagiarism detection | docs.copyleaks.com release notes; copyleaks.com/codeleaks | 9 November 2026 |
| ContentDetector.ai web tool (Content Detector AI card) | Redirecting by 18 August 2026; no statement published | contentdetector.ai returns 301 to the AI Content Detector Mod on the Moxby marketplace, the same Mod the BrandWell page resolves to; the Wayback Machine CDX index shows a 200 capture on 11 May 2026 and 301s on 18 August and 11 October 2026, with an earlier 301 period from July to August 2025; the archived page said the tool was "powered by Content at Scale's AI Detector", so the detector lives on under the Mod and this is a redirect, not a stated withdrawal | moxby.com/marketplace/ai-content-detector; web.archive.org capture of 11 May 2026 | 9 November 2026 |
| Wordtune AI Content Detector (Wordtune card) | 404 since 26 July 2025 (Wayback CDX); no statement published | wordtune.com/ai-content-detector returned 200 in captures through 30 March 2025 and 404 from 26 July 2025; on 10 November 2026 it serves a Webflow 404 page, the widget's Heroku host returns 404, and the site footer still links the dead address; the August 2023 launch post remains live | web.archive.org capture of 30 March 2025; wordtune.com/ai-content-detector | 10 November 2026 |
| Check For AI (CheckforAi) (Check For AI card) | Sunset between 3 June and 23 July 2023 | "We will be sunsetting CheckForAi soon to focus on new projects" (capture of 3 June 2023); "CheckforAi was a free nonprofit project for individuals. We have sunset the service to focus on new projects" (23 July 2023 through the latest capture of 17 June 2026); the host timed out on 10 November 2026 | web.archive.org capture of 27 May 2023 | 10 November 2026 |
| Writefull GPT Detector (Writefull card) | Discontinued between 31 December 2024 and 7 March 2025 | "Our GPT Detector has been discontinued" (route title in the bundle captured 7 March 2025); the live route reads "AI detection tools have high error rates [...] Because of this, we've decided to take our GPT Detector offline" | x.writefull.com/gpt-detector; web.archive.org capture of 31 December 2024 | 10 November 2026 |
| Passed.ai (Passed.ai card) | Closing: registration closed by 10 November 2026; subscriptions end at the close of their billing period | "Passed.ai is closing, the team has joined Originality.ai"; "We're no longer selling or supporting new Passed.ai accounts"; "Existing customers can still sign in at app.passed.ai for the rest of their current term", on every path of the site | passed.ai | 10 November 2026 |
| GPT Radar (GPT Radar card) | Redirecting since 14 August 2026 (Wayback CDX); no statement published | The Wayback Machine holds 200 responses for gptradar.com through 12 July 2026 and 301 redirects to neuraltext.com on 14 August and 8 October 2026; the host did not resolve on 10 November 2026 and the Neuraltext home page does not mention the tool | web.archive.org CDX; web.archive.org, 12 July 2026 | 10 November 2026 |
| Grammica AI Detector (Grammica card) | Removed between 15 December 2025 and 12 January 2026 (Wayback captures); no statement published | The home page capture of 15 December 2025 still links the detector, the relaunched home page of 12 January 2026 does not, and grammica.com/ai-detector returned HTTP 307 to the home page on 10 November 2026; the last 200 capture of the detector page is dated 31 July 2025 | web.archive.org, 15 December 2025; web.archive.org, 12 January 2026 | 10 November 2026 |
| AI Writing Check (AI Writing Check card) | August 2023 (launched January 2023) | "August 2023 Update - AI Writing Check is no longer available"; the capture of 17 July 2023 shows the working tool and the capture of 12 September 2023 the notice | aiwritingcheck.org; web.archive.org, 17 July 2023 | 10 November 2026 |
Each statement is quoted from the page linked in its row, with the date the index read it. No tool is listed on the strength of a news report or a third-party review. A fifth-wave card adds a fourth withdrawal with a vendor statement: Copyleaks withdrew AI detection for source code from its API in two dated release notes, on 28 August 2025 and 16 December 2025, while the Codeleaks product and the text detector continue, so the row names the feature and not the company (Codeleaks card). Two fourth-wave cards are recorded here with care: the DetectGPT demo is gone with no statement, so the row carries the archive dates and not a reason; the BrandWell page redirects rather than closes. A third, Deepware Scanner, is not in the table at all: scanner.deepware.ai did not answer from two networks on 9 November 2026 and its Google Play listing returned 404, so the Deepware card records the host as unreachable at the read date, which is an observation about one day and not a shutdown (deepware.ai, read 9 November 2026).
Why was OpenAI's AI Text Classifier withdrawn?
For low accuracy, in OpenAI's own words. The classifier was released on 31 January 2023 with a published true positive rate of 26% and a false positive rate of 9% on the company's own evaluation set, and the same page states that as of 20 July 2023 the tool "is no longer available due to its low rate of accuracy", with OpenAI turning to research on provenance techniques (openai.com, read 8 November 2026; the OpenAI classifier record). Four independent records in the index tested it before the withdrawal: Weber-Wulff 2023 scored it at 29 of 54 documents correct (54%) (DOI 10.1007/s40979-023-00146-z, read 8 November 2026), and Walters 2023, Elkhatat 2023 and Chaka 2023 carry further counts on their records. The tool has no card because the index cards only detectors a reader can still reach; its figures live on the study record instead. OpenAI's other detector, the 2019 GPT-2 Output Detector, is a different model and has its own card.
When was Writer's AI content detector shut down?
On 22 December 2025, per the vendor's own banner. The archived detector page of 9 December 2025 reads "Important update: This tool will be sunset on December 22 along with the AI detection API endpoint", and the developer documentation captured on 13 December 2025 says the endpoint "is deprecated and will be removed on December 22, 2025" (archived detector page; archived API page, read 9 November 2026). Since 24 December 2025 writer.com/ai-content-detector has returned a redirect to the home page, and the vendor's live plans page mentions no AI detection (writer.com/plans, read 9 November 2026). Writer was tested in 4 indexed records: Weber-Wulff 2023 (27 of 54 correct, 1 false accusation in 18), Walters 2023 (14% of 42 human papers called AI, the joint highest false positive rate of 16 tools), Elkhatat 2023 and Chaka 2023 (Writer card). The card stays in the index because those four results are still cited, and it carries the withdrawal in its own fields.
Is the GPT-2 Output Detector still available?
The code is; the hosted demo is not. OpenAI released the RoBERTa-based detector on 5 November 2019 with the 1.5B-parameter GPT-2 model and a stated detection rate of about 95% on GPT-2 text (openai.com, read 9 November 2026). The hosted demo at openai-openai-detector.hf.space, the address every indexed study used, shows a paused state as of 9 November 2026, the GitHub repository is archived with a last commit of 13 December 2023, and the weights remain on Hugging Face under the MIT License, so a reader runs the model locally with python -m detector.server detector-base.pt (detector README; model card, read 9 November 2026). No pause date is published, so the table records the state at the read date and nothing more. The tool is the second most-tested card in the index, with 9 records (independently tested ranking), and the open-source view carries its repository and licence.
Which other tools in the studies have gone quiet?
Several, but none with a vendor statement the index can quote, so none is in the table. Weber-Wulff 2023 tested 14 tools, of which 6 had a card when this page was written, 9 on 9 November 2026 and 10 on 10 November 2026, as the Weber-Wulff roster question lists with each tool's status; the record's "no card" rows included Check For AI, Crossplag and Writeful GPT Detector until 10 November 2026, when Check For AI and Writefull received cards in the tenth wave and joined the table above as withdrawals (12 of the 14 now carded; PlagiarismCheck received a card the same day in the ninth wave and is live); Compilatio, Content at Scale (now BrandWell) and DetectGPT received cards on 9 November 2026 in the fourth wave (Weber-Wulff 2023 record). Walters 2023 tested 16 tools, 14 of which have a card since GPT Radar, Grammica, IvyPanda and SEO.ai joined on 10 November 2026 with the eleventh wave (two of the four, GPT Radar and Grammica, as withdrawals in the table above), and 10 of which had one since Content Detector AI's was added on 10 November 2026 (its redirect is in the table above), and its "no card" rows include Crossplag, Grammica, GPT Radar and IvyPanda (Walters 2023 record). Orenstrakh 2023 ran CheckForAI alongside the index cards (Orenstrakh 2023 record). The index has read no vendor statement from any of those companies announcing a closure, so their status is unrecorded here rather than asserted; the editors' register lists the detectors still to be read and carded, and a tool found withdrawn when its card is researched will join this table with its statement.
The pattern across the three listed withdrawals is the same: the maker, not an outside tester, decided the tool should stop, and in two of the three cases the maker gave a reason on the page. The fourth, Copyleaks' AI code verdict, follows it: the release notes state what changed and when, and give no reason. OpenAI named accuracy. Writer named no reason in the banner and its privacy policy, effective 17 April 2026, still states that inputs are never used to train its models (writer.com/legal/privacy, read 9 November 2026). The GPT-2 demo's pause has no statement at all.
No detector score should be the only evidence in a misconduct, hiring or publishing decision, and a score from a withdrawn tool cannot be reproduced today.
The launch year ranking, added 10 November 2026, sets each withdrawal in this table beside the year the tool launched, so a reader can see how long each ran: AI Writing Check seven months, Wordtune about two years, Writer and GPT Radar longer.
Two of the rows above were nonprofit tools, AI Writing Check and Check For AI, and the nonprofit and education question records them as the only cards whose free use rested on a nonprofit; the 2027 census counts the twelve withdrawn, unreachable or redirected cards as a share of the index, read 10 November 2026.
Questions about withdrawn AI detectors
Does OpenAI have an AI detector now?
Not a live one. The AI Text Classifier was withdrawn on 20 July 2023 for low accuracy (openai.com, read 8 November 2026), and the 2019 GPT-2 Output Detector's hosted demo is paused, with the code and weights still public under the MIT License (github.com, read 9 November 2026).
Why does the index keep a card for Writer's detector?
Because 4 indexed studies tested it and still cite it: Weber-Wulff 2023, Walters 2023, Elkhatat 2023 and Chaka 2023 (Writer card). The card records the sunset of 22 December 2025 in its ownership, API and free tier fields, read 9 November 2026, so the results keep their context.
How many study records involve a withdrawn tool?
Ten of the 35 records as of 9 November 2026: the OpenAI classifier appears in Weber-Wulff 2023, Walters 2023, Elkhatat 2023, Chaka 2023 and Orenstrakh 2023 and has its own record; Writer appears in the first four of those; the GPT-2 Output Detector appears in 9 records, several shared with the two above. The count is of records, not of tools per record.
Were any of the withdrawn detectors accurate in the studies?
Not by the figures the records print. The OpenAI classifier scored 54% in Weber-Wulff 2023 (DOI 10.1007/s40979-023-00146-z, read 8 November 2026); Writer scored 50% in the same study and called 14% of 42 human papers AI in Walters 2023 (DOI 10.1515/opis-2022-0158, read 9 November 2026). The GPT-2 Output Detector's record runs from 0 of 10 false accusations in Perkins 2024 to 0.9503 of 1,992 in Jabarian and Imas 2025 (false positive rate ranking).
Sources
- OpenAI, New AI classifier for indicating AI-written text, with the 20 July 2023 update: https://openai.com/index/new-ai-classifier-for-indicating-ai-written-text/ (read 8 November 2026)
- OpenAI, GPT-2 1.5B release (5 November 2019): https://openai.com/index/gpt-2-1-5b-release/ (read 9 November 2026)
- Writer AI Content Detector, archived 9 December 2025: http://web.archive.org/web/20251209115654/https://writer.com/ai-content-detector/ (read 9 November 2026)
- Writer AI detection API, archived 13 December 2025: http://web.archive.org/web/20251213021511id_/https://dev.writer.com/home/ai-detect (read 9 November 2026)
- Writer legacy API reference: https://dev.writer.com/api-reference-legacy/content/detect-if-the-content-is-ai-generated (read 9 November 2026)
- Writer plans: https://writer.com/plans/ (read 9 November 2026)
- Writer privacy policy: https://writer.com/legal/privacy/ (read 9 November 2026)
- GPT-2 Output Detector hosted demo: https://openai-openai-detector.hf.space/ (read 9 November 2026)
- GPT-2 output dataset repository and detector README: https://github.com/openai/gpt-2-output-dataset/tree/master/detector (read 9 November 2026)
- RoBERTa base OpenAI detector model card: https://huggingface.co/openai-community/roberta-base-openai-detector (read 9 November 2026)
- Weber-Wulff et al. 2023: https://doi.org/10.1007/s40979-023-00146-z (read 8 November 2026)
- Walters 2023: https://doi.org/10.1515/opis-2022-0158 (read 9 November 2026)
Revision log: 2026-11-09: page created from the index record at version 2026.11.4; 2026-11-09: DetectGPT demo and BrandWell redirect rows added, Deepware noted as unreachable at the read date, Weber-Wulff and Walters card counts updated for the fourth wave.; 2026-11-09: Copyleaks AI source code detection row added from the release notes of 28 August and 16 December 2025 (fifth wave).; 2026-11-09: Weber-Wulff card count brought to 9 and the roster question linked (eighth wave); 2026-11-10: ContentDetector.ai redirect row added from the Wayback CDX record and the Moxby target; PlagiarismCheck and Content Detector AI carded in the ninth wave, Weber-Wulff and Walters card counts updated; 2026-11-10: Wordtune (404 since 26 July 2025 per the CDX), Check For AI (sunset notice 2023), Writefull (discontinuation notice) and Passed.ai (closing notice) rows added from the tenth-wave cards; 2026-11-10: GPT Radar, Grammica and AI Writing Check rows added from the Wayback CDX record and the vendor notice (eleventh wave); Walters card count brought to 14; 2026-11-10: twelfth-wave pages linked
Related pages: Do AI detectors store the text you paste? Every retention clause in the index, quoted and dated, Do AI detectors work on machine-translated text? What two studies measured, with bases, AI detectors ranked by independent testing Two records added in the fifth wave on 9 November 2026, Pegoraro 2023 and Fleckenstein 2024, changed nine counts and none: Pegoraro 2023 tested ZeroGPT, GPTZero, Copyleaks, Originality.ai, Writer, Content at Scale (BrandWell), DetectGPT, the GPT-2 Output Detector and GLTR, lifting GPTZero to 12, the GPT-2 Output Detector to 10, Copyleaks to 7 and Originality.ai and ZeroGPT to 6; Fleckenstein 2024 tested 289 teachers and no software, so it counts for no card ([Fleckenstein 2024 record](/studies/fleckenstein-2024-teachers/)). Illuminarty, one of four cards added in the same wave, joined with its one image record from Ha and Passananti 2024, so 18 of 72 cards now qualify. and Questions about AI detectors, answered from the index.