Which AI detectors have a free API tier? The ten vendors whose free allowance covers API calls, and the twenty that sell an API with no free tier
Ten of the 72 AI detectors in the index state a free allowance that applies to API calls, by the free tier and plans fields of every card read 8 and 9 November 2026 in the data file: Sapling gives a new API key 50,000 characters a day and 250,000 characters a month (sapling.ai, read 8 November 2026), AI or Not's Free plan includes an API key, $5 in credits and 1M words of text detection a month (aiornot.com, read 9 November 2026), Quetext's Developer API starts with 5,000 free words (quetext.com, read 9 November 2026), and Sightengine's Free Tier covers 2,000 operations a month, 500 a day, "for testing the API and proofs of concept" (sightengine.com, read 9 November 2026). 39 cards state an API in all; the other 20 sell it on a paid plan or by contact and state no free API allowance, and 12 cards state no API.
A free web check and a free API call are different offers, and the table keeps them apart. Phrasly, Scribbr, Surfer and Smodin give away web checks with no stated cap, but the question here is whether a developer can call the detector from code without paying, and only the vendor's own words settle it: a free plan that says "API key included", an API page that says "free words to start", or a changelog line about new keys. Rows quote the free tier or plans field of the card, name what the allowance scores and the first paid API price on the same page, and link the page with its read date. This page is one of the questions answered from the index; the API pricing ranking orders the paid rates per 1,000 words, the API view lists every card with an endpoint and its documentation link, and the AI detector register carries every card.
| Detector | Free allowance on the API, as the vendor states it | What the allowance scores | First paid API price stated | Source | Read date |
|---|---|---|---|---|---|
| Sapling | "API: new keys get 50,000 characters/day and 250,000 characters/month" | Text | From $0.005 per 1,000 characters, one-time $5 minimum | sapling.ai | 8 November 2026 |
| AI or Not | "Free plan: $5 in free credits, 1M words of AI text detection free every month, 20 AI image checks, API key included" | Text, images | Pro $5 a month with $10 in credits; pay as you go $5 per million words of text | aiornot.com | 9 November 2026 |
| Quetext | Developer API: "5,000 free words to start" | Text (AI and plagiarism reports) | $0.10 per 1,000 words analyzed, prepaid wallet | quetext.com | 9 November 2026 |
| Winston AI | "API: register for free and receive 2,500 credits" | Text, images | Essential $18 a month ($9 with code WINSTON50), 100,000 credits | gowinston.ai | 8 November 2026 |
| Proofademic | "API: 2,000 trial credits (1 credit = 1 word)" | Text | Essential $15 a month, 200,000 words | proofademic.ai | 8 November 2026 |
| Walter Writes | "API: start on the free tier"; the page states no size for it | Text, images, voice | API plans from $49 a month for 300K words | walterwrites.ai | 8 November 2026 |
| TruthScan | Free plan, $0 a month: "25 results a month (images plus PDF pages) ... full API access"; text is billed at 1 credit per word with no free word allowance stated | Images, PDF pages; text by credit | Starter $24 a month, 1,000 results; Enterprise "$0.005 or less per result" | truthscan.com | 9 November 2026 |
| Sightengine | "Free Tier: 2,000 operations a month (maximum 500 a day) ... for testing the API and proofs of concept" | Images, video, deepfakes | Starter $29 a month, 10,000 operations, $0.002 per additional operation | sightengine.com | 9 November 2026 |
| Reality Defender | "Free API plan: $0/month, 50 scans per month, up to 3 seats, image analysis only, API keys and an analytics dashboard" | Images (audio and video need a paid plan) | Business $399, annual billing, 1,000 scans a month | realitydefender.com | 9 November 2026 |
| WasItAI | "Free: $0/month, 10 images per month, API access, browser extension" | Images | Basic $3.99 a month, 100 images | wasitai.com | 9 November 2026 |
Allowances as each vendor states them on the page linked, read on the date shown; the index has not called any of the ten APIs.
Which AI detector APIs can you call for free?
Ten, and six of them score text. Sapling's allowance is the only one stated per day and per month in the unit the API bills, characters: 50,000 a day and 250,000 a month on a new key, against a paid rate from $0.005 per 1,000 characters with a one-time $5 minimum (sapling.ai, read 8 November 2026). AI or Not states the largest text figure, 1M words of AI text detection a month on the Free plan with an API key included and $5 in credits, where the Pro pay-as-you-go rate is $5 per million words (aiornot.com, read 9 November 2026). Quetext gives 5,000 free words on the Developer API before the $0.10 per 1,000 words wallet rate applies (quetext.com, read 9 November 2026). Winston AI grants 2,500 credits on free API registration, separate from the 2,000-credit, 14-day web trial (gowinston.ai, read 8 November 2026). Proofademic grants 2,000 trial credits at one credit a word (proofademic.ai, read 8 November 2026), and Walter Writes says the API starts on a free tier without stating its size (walterwrites.ai, read 8 November 2026).
The other four are media detectors. Sightengine's 2,000 operations a month, capped at 500 a day, cover AI image and video detection and basic moderation (sightengine.com, read 9 November 2026); Reality Defender's Free API plan gives 50 image scans a month on up to 3 seats (realitydefender.com, read 9 November 2026); WasItAI gives 10 images a month with API access (wasitai.com, read 9 November 2026). TruthScan sits between the groups: its Free plan states "full API access" and 25 results a month, where a result is an image or a PDF page, and its text endpoint bills one credit per word with no free word figure on the pricing page (truthscan.com, read 9 November 2026).
Which text detector gives the largest free API allowance?
AI or Not, at 1M words a month, by the figure on its pricing page, read 9 November 2026. At 5.5 characters a word, the conversion the API pricing ranking uses, Sapling's 250,000 characters a month come to about 45,000 words, Quetext's 5,000 words and Proofademic's 2,000 credits are one-time starts, and Winston AI prices its 2,500 credits in credits rather than words. None of the six text vendors publishes an accuracy figure for API results as distinct from the web tool, and the test record behind the six is thin: Sapling has 3 study records and Winston AI 2 in the ranking by independent testing, while AI or Not's one record is an image test, Ha and Passananti 2024, which recorded a 24.47% false positive rate on 280 human artworks for the tool under its earlier name Optic (DOI 10.1145/3658644.3670306, read 9 November 2026). Proofademic, Quetext and Walter Writes have no study record.
Which detectors sell an API with no free tier?
Twenty cards state an API and no free allowance for it. Six of the twenty give away web checks and charge for every API call: Pangram's free plan is 20 checks a day on the web while its API bills $0.05 per 100 words, with $10 of API credits inside the $20 Individual plan (pangram.com, read 8 November 2026); ZeroGPT's free plan allows 1,250,000 words a month on the web and prices the API from $0.042 per 1,000 words (zerogpt.com, read 8 November 2026); Phrasly's free detector has no limit while its Business API costs $100 a month (phrasly.ai, read 8 November 2026); Undetectable AI's web detector takes 10,000 words a check for nothing while API Starter costs $29 a month (undetectable.ai, read 9 November 2026); GPTZero's free plan covers 10,000 words a month on the web (gptzero.me, read 8 November 2026); Originality.ai gives 10K words one time and reserves API access for Enterprise plans from $136.58 a month (originality.ai, read 8 November 2026). Two open-source cards, GLTR and the GPT-2 Output Detector, have no hosted API tier at all; their code runs on the reader's machine, as the offline detectors question sets out. Resemble Detect's Flex plan has no subscription fee and API access, but bills from the first credit at $0.035 per second of audio (resemble.ai, read 9 November 2026), so it is counted here as paid.
Cards with an API and no free API allowance stated
| Detector | Free tier as stated | API route as stated | Source | Read date |
|---|---|---|---|---|
| Pangram | 20 free credits daily on the web | Text $0.05 per 100 words; $10 of API credits in the $20 Individual plan | pangram.com | 8 November 2026 |
| GPTZero | Free plan, 10,000 words a month on the web | API documented at docs.gptzero.me; plan cards did not render | gptzero.me | 8 November 2026 |
| Copyleaks | A limited number of free credits, count not published | Personal $16.99 a month for 100 credits, 1 credit per 250 words | copyleaks.com | 8 November 2026 |
| Phrasly | Free web detector with no limit | Business API $100 a month including $100 in credits; $0.02 per 1,000 words | phrasly.ai | 8 November 2026 |
| Originality.ai | 10K words (100 credits) one time | API access on Enterprise plans from $136.58 a month; $0.01 per 100 words | originality.ai | 8 November 2026 |
| ZeroGPT | 1,250,000 words a month on the web | API pay as you go from $0.042 per 1,000 words | zerogpt.com | 8 November 2026 |
| Hive | Free Chrome extension and Hive Detect web tool, no cap stated | Every AI detection pricing line is Contact Sales | deploy.com | 8 November 2026 |
| GLTR | Free and open source | Local server from the repository; no hosted API tier | github.com | 9 November 2026 |
| GPT-2 Output Detector | Free and open source | Local server from the repository; hosted demo paused | github.com | 9 November 2026 |
| Codequiry | Free plan covers peer similarity only; AI detection excluded | Grow US$200 a month base, 20 web and AI checks; API and CLI included | codequiry.com | 9 November 2026 |
| Undetectable AI | Free web detector, up to 10,000 words a check | API Starter $29 a month, 72,500 words, then $0.40 per 1K words | undetectable.ai | 9 November 2026 |
| Smodin | Free web checks, 50,000 characters a check | API access on Premium, $19.99 a month; separate API pricing page | smodin.io | 9 November 2026 |
| Surfer | Free web detector, no limit stated | API access on Peace of Mind, 299 USD a month billed yearly | surfer.ai | 9 November 2026 |
| Compilatio | None for the detector | API with Magister+, by demo and quote | compilatio.net | 9 November 2026 |
| Deepware | Free web scanner (BETA), no quota published | API key and SDK by contact | deepware.ai | 9 November 2026 |
| Sensity | None published | Cloud platform and API by sales; accounts held for manual review | sensity.ai | 9 November 2026 |
| Codeleaks | None published for Codeleaks | Enterprise, Talk to Sales | copyleaks.com | 9 November 2026 |
| Illuminarty | Free plan, web app classification | API usage from Basic, $10 a month, 10,000 requests a day | illuminarty.ai | 9 November 2026 |
| Pindrop Pulse | None published | Demo and sales; batch API on Pulse Inspect | pindrop.com | 9 November 2026 |
| Resemble Detect | Flex $0 a month, no subscription fee; "first detection for free", no allowance stated | Prepaid credits from $0.035 per second of audio and per image | resemble.ai | 9 November 2026 |
Free tiers and API routes as the free tier and plans fields of each card record them, read on the date shown. The 12 cards with no API field are QuillBot, Grammarly, Scribbr, JustDone, Turnitin, AIDetectPlus, Writer, Grammarly Authorship, Turnitin Clarity, SynthID, BrandWell and DetectGPT.
A free API allowance measures how much a developer can test for nothing; it says nothing about what the API returns, and six of the ten cards that offer one have no study record.
Sapling's free API allowance and GPTZero's documented API are compared on 14 fields in the Sapling vs GPTZero comparison, read 10 November 2026.
Questions about free AI detector APIs
Is there an AI detector with a free API?
Ten of 42 cards state one, read 8 and 9 November 2026: Sapling (250,000 characters a month on a new key), AI or Not (1M words a month with an API key), Quetext (5,000 words to start), Winston AI (2,500 credits), Proofademic (2,000 credits), Walter Writes (size not stated), TruthScan (25 results a month), Sightengine (2,000 operations a month), Reality Defender (50 image scans a month) and WasItAI (10 images a month).
Which free AI detector API allows the most text?
1M words a month, on AI or Not's Free plan with an API key included (aiornot.com, read 9 November 2026). Sapling's 250,000 characters a month come to about 45,000 words at 5.5 characters a word (sapling.ai, read 8 November 2026).
Does GPTZero or Originality.ai have a free API?
10,000 words a month on the web is GPTZero's free allowance (gptzero.me, read 8 November 2026) and 10K words one time is Originality.ai's, with API access reserved for Enterprise plans from $136.58 a month (originality.ai, read 8 November 2026); neither page states a free API allowance.
Which free AI detector APIs score images rather than text?
Four of the ten: Sightengine (2,000 operations a month), Reality Defender (50 image scans a month), WasItAI (10 images a month) and TruthScan (25 results a month, images plus PDF pages), by their pricing pages read 9 November 2026. AI or Not and Winston AI score both text and images on their free API allowances.
Has any free-API detector been tested by a study?
4 of the 10 have a study record: Sapling 3, Winston AI 2, AI or Not 1 and Sightengine 1, by the study lists on their cards read 9 November 2026. AI or Not's and Sightengine's records are image tests; Proofademic, Quetext, Walter Writes, TruthScan, Reality Defender and WasItAI have none.
Sources
All read 9 November 2026 unless an earlier date is shown; the source of every row is linked in the tables.
- Sapling pricing: https://sapling.ai/pricing (read 8 November 2026)
- AI or Not pricing: https://www.aiornot.com/pricing
- Quetext pricing: https://www.quetext.com/pricing
- Winston AI pricing: https://gowinston.ai/pricing/ (read 8 November 2026)
- Proofademic pricing: https://proofademic.ai/pricing/ (read 8 November 2026)
- Walter Writes home page: https://walterwrites.ai/ (read 8 November 2026)
- TruthScan pricing: https://truthscan.com/pricing
- Sightengine pricing: https://sightengine.com/pricing
- Reality Defender API: https://www.realitydefender.com/api
- WasItAI API: https://wasitai.com/api
- Pangram pricing: https://www.pangram.com/pricing (read 8 November 2026)
- GPTZero pricing and free plan: https://gptzero.me/pricing and https://gptzero.me/news/best-ai-detectors (read 8 November 2026)
- Copyleaks pricing: https://copyleaks.com/pricing (read 8 November 2026)
- Phrasly pricing: https://phrasly.ai/pricing?plan=monthly (read 8 November 2026)
- Originality.ai pricing: https://originality.ai/pricing (read 8 November 2026)
- ZeroGPT pricing: https://www.zerogpt.com/pricing (read 8 November 2026)
- Deploy (Hive) pricing: https://deploy.com/pricing (read 8 November 2026)
- GLTR repository: https://github.com/HendrikStrobelt/detecting-fake-text
- GPT-2 Output Detector README: https://github.com/openai/gpt-2-output-dataset/tree/master/detector
- Codequiry pricing: https://codequiry.com/pricing
- Undetectable AI pricing: https://undetectable.ai/pricing
- Smodin pricing: https://smodin.io/pricing
- Surfer pricing: https://surfer.ai/pricing/
- Compilatio API: https://www.compilatio.net/en/plagiarism-detection-api/
- Deepware FAQ: https://deepware.ai/us/faq/index.html
- Sensity: https://sensity.ai/
- Copyleaks Codeleaks: https://copyleaks.com/codeleaks
- Illuminarty: https://illuminarty.ai/en/
- Pindrop Pulse Inspect launch: https://www.pindrop.com/company-news/pindrop-launches-pulse-inspect
- Resemble AI pricing: https://www.resemble.ai/pricing
- Ha and Passananti 2024: https://doi.org/10.1145/3658644.3670306
Revision log: 2026-11-09: page created from the free tier, plans and api fields of 42 cards at index version 2026.11.7; 2026-11-10: twelfth-wave pages linked
Related pages: Which AI detectors detect AI-paraphrased text? The 16 vendors that claim it, the 5 that report it as a label or setting of its own, and what 11 studies measured, Which AI detectors were tested on GPT-4 text? The 13 cards scored on GPT-4 family output in 7 study records, with every result and its base, AI detector APIs ranked by published price per 1,000 words and Questions about AI detectors, answered from the index.