Is there an AI detector for short texts? Every stated minimum length in the index

Phrasly, at 30 words on the web tool and 50 on its Business API (phrasly.ai, read 8 November 2026); Sapling, which says results are "more accurate after about 50 words" and recommends at least 300 characters on its API, flagging anything under 500 characters low_confidence (sapling.ai, read 8 November 2026); AI or Not, whose text API takes text from 250 characters, about 64 words (docs.aiornot.com, read 9 November 2026); and QuillBot at 80 words per scan (quillbot.com, read 8 November 2026). Copyleaks states 255 characters on its web platform, about 46 words, and 350 in its browser extension (copyleaks.com, read 8 November 2026). A floor is where the vendor lets the check run, not where the vendor says it is accurate: Phrasly's 30 words carry the qualifier "for accurate results", and the Phrasly card has no study record at any length.

The marketplaces and review platforms view, added 9 November 2026, reads these minimums for one reader: a platform scoring product reviews at volume, which needs an API and a bulk route beside a minimum under 300 characters, a combination only Phrasly and Sapling state.

Turnitin requires at least 300 words of prose in a long-form writing format and does not process a submission below it (guides.turnitin.com, read 8 November 2026); Turnitin Clarity shows AI writing results only on a pasted block of 300 or more words when the Originality add-on is licensed (guides.turnitin.com, read 9 November 2026). Smodin's input box requires 1,000 characters, about 182 words (smodin.io, read 9 November 2026); Surfer's help centre says text "must be at least 100 words long for a scan to run" (surfer.ai, read 9 November 2026); Originality.ai sets a 100-word minimum (originality.ai, read 8 November 2026); JustDone names 350 characters for reliable results (justdone.com, read 8 November 2026). A tweet, a text message or a one-line email answer falls under every one of these floors.

OpenAI's announcement of its 2023 classifier is the one vendor statement in the index that puts a number on length: the classifier was "very unreliable" on texts under 1,000 characters, reliability "typically improved as input length increased", and the tool identified 26% of AI-written text while mislabelling human text 9% of the time before it was withdrawn in July 2023 (openai.com, read 8 November 2026; OpenAI classifier record). Smodin's detector page says a passage that looks "brief, standardized, and mechanically polished" can be labelled machine-written (smodin.io, read 9 November 2026), and the Moxby listing for BrandWell's detector says human text can be flagged "especially when it is short, technical, templated, highly edited" (moxby.com, read 9 November 2026).

The indexed studies tested long text. Weber-Wulff 2023 wrote its human documents at about 10,000 characters and set a 2,000-character minimum for its ChatGPT documents (arXiv 2306.15666, read 8 November 2026; Weber-Wulff 2023 record); Perkins 2024 started from 15 AI texts of about 500 words each (arXiv 2403.19148, read 8 November 2026; Perkins 2024 record); Chaka 2023 ran 21 whole chatbot responses and 30 translations and prints no word counts (DOI 10.37074/jalt.2023.6.2.12, read 9 November 2026; Chaka 2023 record). One of the 35 records scored detectors on texts under 250 words: Jabarian and Imas 2025 recorded false positive rates of at most 0.0250 for Pangram and 0.0333 for GPTZero on 160 human stubs under 50 words per model, and excluded Originality.ai from that test because its API returned a length filter error (NBER w34223, Table B.1, read 9 November 2026; Jabarian and Imas 2025 record). No other record scored texts under 250 words, so the index holds no short-text false positive or false negative rate for any other card, and the ranking by independent testing says nothing about length.

Cards that state no minimum

A fact desk checking a tip or a quote reads the same floors with a second condition, an API or browser extension: the newsrooms view, added 9 November 2026, finds 5 cards stating both.

All read 8 November 2026 unless a later date is shown; the input limits source of every card is linked in the tables.

• Phrasly AI detector: https://phrasly.ai/ai-detector
• Sapling AI detector: https://sapling.ai/ai-content-detector
• QuillBot AI detector: https://quillbot.com/ai-content-detector
• Copyleaks AI detector: https://copyleaks.com/ai-content-detector
• Originality.ai pricing: https://originality.ai/pricing
• JustDone AI detector: https://justdone.com/ai-detector
• Turnitin AI writing detection FAQs: https://guides.turnitin.com/hc/en-us/articles/28477544839821
• Turnitin Clarity instructor FAQs: https://guides.turnitin.com/hc/en-us/articles/37198804513165-FAQs-for-Instructors-using-Turnitin-Clarity (read 9 November 2026)
• Smodin AI detector: https://smodin.io/ai-content-detector (read 9 November 2026)
• Surfer AI detector: https://surfer.ai/ai-content-detector/ (read 9 November 2026)
• AI or Not text API: https://docs.aiornot.com/api-reference/reports-by-modality/image (read 9 November 2026)
• Moxby AI Content Detector Mod (BrandWell): https://moxby.com/marketplace/ai-content-detector/ (read 9 November 2026)
• OpenAI, New AI classifier for indicating AI-written text (31 January 2023): https://openai.com/index/new-ai-classifier-for-indicating-ai-written-text/
• Weber-Wulff et al. 2023: https://arxiv.org/pdf/2306.15666
• Perkins et al. 2024: https://arxiv.org/pdf/2403.19148
• Chaka 2023: https://doi.org/10.37074/jalt.2023.6.2.12 (read 9 November 2026)

Revision log: 2026-11-09: page created from the input limits field of 38 cards at index version 2026.11.5; 2026-11-09: marketplaces and review platforms view linked (fifth wave); 2026-11-09: link to the minimum input ranking added; 2026-11-09: character conversions moved from 6 to 5.5 characters a word (Copyleaks 255 characters about 46 words, Smodin 1,000 about 182) under the one-rate rule, and the Jabarian and Imas 2025 stub test under 50 words added to the studies paragraph and the lead (seventh wave); 2026-11-09: eighth-wave pages linked