leo malettadiocionou a nota a year ago

в каком контексте?

https://books.google.com/ngrams/graph?content=can+tell+from%2C+can+tell+by&year_start=1800&year_end=2019&corpus=en-2019&smoothing=3

So they're mostly interchangable, thanks grumbler

Not sure - check the examples. Possibly, there is a slight difference.

https://forum.wordreference.com/threads/tell-by-tell-from.2177248/
here they say no difference

As with everything, the difference lies in the context. In a passive scenario — one where the speaker notices something without actively looking for it — both forms are used, but FROM is more contextually appropriate: "I can tell FROM/by his eyes that he's been smoking." (=the speaker casually noticed that he'd been smoking when she looked into his eyes by chance).

However, when the speaker actively uses something as a gauge or indicator, BY expresses agency more readily than FROM: "I can tell BY looking into his eyes if he's been smoking." (=when I want to know if he's been smoking, I look into his eyes). The option FROM LOOKING would be incorrect here, although it's POSSIBLE if it's "shorthand" for FROM HAVING LOOKED: [doctor]: "I can tell from looking at your xrays last month, that you're developing glaucoma."

Finally, I think it's worth making a distinction here. You can tell something FROM EXPERIENCE, but BY INTUITION. Even a lot of natives get this wrong.

https://books.google.com/ngrams/graph?content=could+tell+from+intuition%2Ccould+tell+by+intuition&year_start=1800&year_end=2019&corpus=en-2019&smoothing=3

https://books.google.com/ngrams/graph?content=could+tell+from+experience%2Ccould+tell+by+experience&year_start=1800&year_end=2019&corpus=en-2019&smoothing=3

However, when the speaker actively uses something as a gauge or indicator, BY expresses agency more readily than FROM:

Uly, what does 'agency' mean here?

Using something to achieve a particular purpose.