--When someone blocks you on WhatsApp it's always ambiguous. There could be more than one reason why the last seen time and Online information is not visible for the contact. Some of the possibilities include, the contact's phone being out of network range, phone switched off or lost, WhatsApp client uninstalled, and of course BLOCKED.

--If both the "last seen at..." and "online" timestamps do not display for one of your contacts, you may have been blocked.

►With WhatsApp Block Detector, you can lookup a contact and see the "last seen at.." and "time elapsed since last seen" ( this feature is not present in WhatsApp ). even if the contact has blocked you. If you do not see the "last seen at.." from the WhatsApp client but in WhatsApp Block Detector it shows as "Last seen" within a reasonable time, then it can be concluded that you have been BLOCKED by the contact.

*Clean and simple to use interface.
* Pickup contacts directly from the phonebook.
* Numbers are validated and formatted automatically. You can use any format that you want without any editing, like +1-XXX, 001-XXXX, local number without country code, numbers with hyphen or space.
* The default country is automatically set based on the sim card location. You can either use the country code in the number or manually switch the country for international numbers.

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Source: https://play.google.com/store/apps/details?id=com.whatsapp.block.detector