AI Checker

You've finished a piece of Japanese writing, something about it reads a little stiff, and you'd like a second opinion before it goes out. Tools that claim to detect AI writing usually present a percentage and let you assume it means something precise. AI Checker, a Japanese-language site, is more careful. Next to its plans it states that the score is not a probability of AI generation and not proof of authorship, and the result panel adds that analysis by a large language model is reference information.

That framing makes it more useful. What you get is a read on how a passage comes across, with reasons.

You paste Japanese text, or load a TXT or Word file, between 100 and 10,000 characters. The free check needs no registration and returns an overall score with the main reasons, grouped under four headings: structure, expression, specificity and consistency. It has usage limits, shown inside the tool.

The paid plans produce a detailed report. It quotes the passages it's commenting on, explains each point, and offers improvement ideas and example rewrites. The site notes that suggestions are never applied automatically and that a person needs to check facts, meaning and sources. Reports can be saved as TXT or PDF.

Free costs nothing. Basic is $9.99 a month, with the first 30 days at $4.99, and covers 60,000 words a month. Pro is $29.99 a month, with the first month at $14.99, and has a higher monthly allowance. By the site's own description, the two paid plans differ only in how much you can analyse.

The tool tells you where your text is headed before you start, which is a nice touch. Pressing the button sends it through the site's server to the provider shown on screen, which is DeepSeek, with Copyleaks named as an alternative. According to the privacy section, the site doesn't store your text or results in its database. For the DeepSeek features, input and output are also sent to a moderation service called Waffo, and a check record without the text is kept for 30 days.

So don't paste anything confidential. The operator is named on the site as Zhi Haosong, a sole proprietor based in Jiangxi, China, with a contact email for support, cancellation and refunds. If you write in Japanese and want to know how a draft comes across, the free check is a quick way to find out.