The best free alternative to DiffBot is UI.Vision RPA, which is both free and Open Source. If that doesn't suit you, our users have ranked more than 50 alternatives to DiffBot and many of them is free so hopefully you can find a suitable replacement. Other interesting free alternatives to DiffBot are Portia (Free, Open Source), Apify (Freemium, Open Source), Diggernaut (Freemium) and Aggregatus (Free).
YabTab automatically converts web pages to tables. There is tonnes of information on web: think of product listing pages, course catalogues, job postings, reports - and all of them are essentially tables.
Dashblock turns websites into APIs thanks to machine learning. Go to a page, right-click on the data you want and save your custom API. That's it, you can now query this API with similar URLs to automatically receive the structured data!