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Blogs exist in many shapes and forms. Researchers are often encouraged to blog as part of their academic outreach and promotion, so the term does not inform you on the authority of a source. The resulting media can fall into different categories:
Blogs focused on a specific subject can be managed by non-experts. A blog being specialised does not mean it is authoritative. You should still assess the quality of such a source.
Blogs are more acceptable when working on a very current issue, for which the academic publishing process has not had time to take place yet. Months if not years can pass between submission and publication of an article in a scholarly journal.
Generally academic blogs will be awarded a status similar to grey literature: they can be cited, but should probably not be your main references. Non-academic blogs would rate lower on the authority scale, close to websites and social media.