Say there are websites example1.com, example2.com, example3.com. Whenever a keyword "keyword1" is posted on example1.com, I need an update to my email(or whatever eg: discord, twitter, facebook).
Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer.– Community BotFeb 13 at 13:19
what's not clear?– catcactcactedFeb 13 at 13:37
Welcome to Software Recommendations! Please note this site is about recommending software, not assets or resources like howtos, manuals/tutorials, code fragments, etc. So what exactly you are looking for: a library (for what environment?), a module/extension (for what framework?) – or something else?– Izzy ♦Feb 13 at 23:23
For highly specific queries, you can build your own modular system consisting of a crawler, indexer and email notifier. If you don't want to build your own crawler you can use any search engine of your choice, and query their index periodically.
I think sending your own reports (frequency, length, formatting...) will remain your own responsibility.
If you want to search some news-sites about some topic, once there was Google News Alerts. Whenever some newspaper/newssite (that doesn't mind being crawled by G.) publishes a new article with a certain keyword, Google will send you mail with a source link and some preview textsnippet.
To a certain extent this is still possible with news.google.com .
In the desktop view, click on "Search for topics, locations and sources", and save your search. However I think they have removed the email notification part (maybe they have replaced it with optional smartphone notifications)
The question is very vague. Various websites present various data in many different ways - some have APIs, some have RSS that you could utilize, other output HTML that can be scraped problemlessly, different ones may require e.g. authenticating to access a certain page.
You also haven't mentioned what kind of software you're looking for. A Windows application that would run in background and do it for you after an easy setup? A Linux-compatible executable that you can set up and run on some server or in Docker? Or perhaps a programming library or framework that would help you to write your own application?
In my opinion the question is unanswerable accurately without knowing these details, but a generic response that would cover most use cases is to use a library like Scrapy in combination with some SMTP/Discord/Twitter/Facebook library, write a fitting code for your use case and run it every X seconds on a server.