Aylien Text Analysis
A collection of information retrieval and natural language APIs
Natural language processing and text analysis.
Cloudmersive Natural Language Processing API is a free Text Analysis API that requires apiKey authentication, is served over HTTPS and supports CORS, so it can be called from the browser.
Details from cloudmersive.com.

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A collection of information retrieval and natural language APIs
The Cloudmersive Natural Language Processing API is provided by Cloudmersive (cloudmersive.com).
Yes. The Cloudmersive Natural Language Processing API is listed in the Text Analysis category of the public-apis directory, which only includes APIs that are free or have a free tier. Check its documentation for rate limits and paid plans.
Yes. The Cloudmersive Natural Language Processing API uses apiKey authentication, so you need to register for credentials before making requests.
Yes. The Cloudmersive Natural Language Processing API supports CORS, so front-end JavaScript can call it directly.
Yes. The Cloudmersive Natural Language Processing API is served over HTTPS, so it's safe to use in production.