You want to base your academic, scientific research on scientifically sound sources. Often, the publisher already gives you an insight into how reliable the source is; publishers of A1-journals, for instance, already peer-review their articles. Academic libraries collect scientific literature, etc.
However, you can also find many interesting sources on the internet. The CRAAP test gives you 5 criteria you should consider critically before using a source for your scientific research.

1. CURRENCY
How recent is the information you found? Look for a date stamp or the last date of an update. 

2. RELEVANCE
How relevant is the information? What does the source say about your research topic? Is the information not too easy or too difficult for the intended audience of your research?

3. AUTHORITY
Who published the information? Did you find it in an A1-publication or in a tabloid? Who is/are the author(s) and can you contact them? Did someone sponsor this article (and if so, who did)?
The URL can tell you a lot about the origins of the information. ".edu," for instance, is used by educational instutitutions and ".fed" by the Belgain governemnt (cf. ".gov" by the US governement).

4. ACCURACY
How accurate is the information in this source? This can be difficult to check, so first look if you can find references and which type of sources they refer to. If you cannot find a list of references or at least a bibliography, the information you found might not be reliable.
If a source is reliable, other websites will link to it. You can look this up by entering this query in Google: “link:[insert url]”.

5. PURPOSE / POINT OF VIEW
All sources have a point of view. What point of view is represented by the source you found? What purpose or goal does the website have? Does it want to inform, or does it want to convince you of their point of view? Even if the author of the piece is a respected researcher, they can still write opinion pieces that want to convince you of something rather than inform you about something so you can draw your own conclusions.

Additional tips for verifying the reliability of the source are:

• Are there a lot of grammar and/or spelling errors?
• Does the source link to different platforms and do those links work?
• Does the layout look neat? Etc.