Best AI Humanizer in 2026

We asked common AI models for 30 texts the way a normal user would: 8 English essay paragraphs, 6 blog posts, 6 work emails, and 5 texts each in Spanish and Brazilian Portuguese, from 156 to 793 words. Some include APA citations, bold text or headings, to see whether a tool keeps them. Each tool got the same texts on its free version with default settings, one at a time, within its free limits.

• Meaning kept. Similarity between each output and its original, from 0 to 1. Above 0.9 means the meaning is close.
• New claims. Facts, numbers, names or examples in the output that were not in the original, plus statements that contradict it. Counted by comparing each output with its source.
• Errors. Spelling and grammar issues found by LanguageTool. The originals had 1.3 per text, mostly false alarms.

Limits of this test: Clever AI Humanizer asked for a human verification check after five texts and HumanizeAI.co’s free words ran out after seven, so their results cover fewer texts. We stop at verification checks and free limits rather than working around them. QuillBot showed a bot check to our test browser, so it is not tested yet.

Spanish and Portuguese (10 texts): our Deep engine had 0.8 spelling and grammar errors per text, the same as the originals. Superhumanizer had 23.7 per text.

What this means: three popular tools added 6 to 10 claims per text that the original never said, from new examples to changed facts. In an essay or a work email, one invented statistic can do more damage than a stiff sentence. Read every output against your draft, whichever tool you use.

1. 1. AI Humanizer (ours)

   Best for keeping your facts, citations and meaning

   We make this one, so weigh our view accordingly. It offers three strengths (Light, Standard and Deep), four modes and four reading levels, keeps citations, links, quotations and any words you choose exactly as written, and checks every run against your original. Free runs need no account.

   From its site:

   1,000 words per run and 2,000 a day free (3,000 with a free account); English, Spanish and Portuguese; built-in AI score from a named third-party detector; paid from $4.99 a month billed yearly.

   Our test:

   Standard: meaning kept 0.967, 0.3 new claims per text. Deep: 1.6 new claims per text; 0.8 spelling and grammar errors per text in Spanish and Portuguese, the same as the originals.

2. 2. Superhumanizer

   Best for fast, generous free runs

   Fast (about 8 seconds a text) and generous for a free tool, with 1,200 words per run and no account. Read every output against your draft: in our test it added claims that were not in the original and sometimes contradicted it. Its Spanish and Portuguese output had many spelling errors.

   From its site:

   Paid plans from $12 a month for 15,000 words, 1,500 words per input; 7-day money-back guarantee.

   Our test:

   Meaning kept 0.912; 6.3 new claims and 2.0 contradictions per text; 23.7 spelling and grammar errors per text in Spanish and Portuguese (originals: 0.8).

3. 3. Clever AI Humanizer

   Best for long texts at no cost

   The most generous free limit we found: up to 3,000 words per request with no fixed monthly allowance, subject to service availability. It was the slowest we tested (about 30 seconds a text), and after five texts it asked for a human verification check.

   From its site:

   Free, up to 3,000 words per request, no paywall stated.

   Our test:

   9.6 new claims and 2.2 contradictions per text on 5 essay texts (ours on the same texts: 0.8 new claims); outputs 16% longer than the originals.

4. 4. HumanizeAI.co

   Best for quick, short edits

   Without an account it worked in pieces of about 300 words, so we pasted long texts paragraph by paragraph. The free words ran out after about 1,800. Outputs came back about a fifth longer than the originals.

   From its site:

   Free plan 2,000 words a month; paid from $9 a month for 15,000 words.

   Our test:

   8.3 new claims and 1.3 contradictions per text on 7 texts (ours on the same texts: 0.6 new claims); outputs about a fifth longer.

5. 5. QuillBot

   Best for people already using QuillBot’s paraphraser and grammar checker

   QuillBot’s humanizer is one tool in a larger writing suite. The free tier covers short texts, and Premium adds advanced humanizing. A good fit if you already pay for Premium.

   From its site:

   Basic humanizing free for short texts; five languages; Premium from $8.33 a month.

   Our test:

   Not tested yet (its tool page showed a bot check).

6. 6. Grammarly

   Best for humanizing inside the Grammarly editor

   Grammarly’s humanizer sits next to its grammar and tone checks. The page tool works without an account, and a free account adds four preset voices and a custom voice.

   From its site:

   Basic tool free without an account; six languages; Pro from $12 a month.

   Our test:

   Not tested yet.

7. 7. Undetectable AI

   Best for a humanizer bundled with a detector

   Undetectable AI pairs its humanizer with an AI detector on every plan. The free trial is short, so expect to pay for regular use.

   From its site:

   Free trial limited to 250 words; from $5.00 a month billed yearly ($60) or $9.99 monthly for 10,000 words a month.

   Our test:

   Not tested yet.

8. 8. GPTHuman

   Best for writing in many languages

   GPTHuman lists 50+ languages on its pricing page and includes limited AI detector use in the free plan. Paid plans raise the length of one output from 300 to 1,000–2,500 words.

   From its site:

   Free trial of 300 words; Starter $8.25 a month billed yearly ($99) or $15 monthly for 25,000 words a month.

   Our test:

   Not tested yet.

9. 9. Walter Writes

   Best for a low yearly price and 80+ languages

   Walter Writes includes an AI detector with every plan and lists 80+ languages. It says it offers free usage but does not state how much.

   From its site:

   Starter $8 a month billed yearly ($96) for 30,000 words a month, 750 words per request.

   Our test:

   Not tested yet.

• Essays, reports and work emails. Pick a tool that keeps your facts and citations, then read the result against your draft. New claims you did not write are the risk that matters most here.
• Long texts on a zero budget. Clever AI Humanizer takes 3,000 words at a time. AI Humanizer takes 1,000 per run and 2,000 a day without an account.
• Spanish or Portuguese. Check spelling in the output. In our test, error counts ranged from 0.8 to 23.7 per text depending on the tool.
• You already pay for a writing suite. QuillBot Premium and Grammarly Pro include a humanizer, so try it before adding another subscription.
• Any tool. No humanizer can promise a pass: detectors disagree with each other and change without notice. Add your own examples and views, which no tool can do for you.