Well, like with most things, it depends.

If you need to know how to read music depends on the style of music that you want to play and your violin goals.

The style of music

If you want to play mostly folk or fiddle music, you do not need to know how to read music. Folk music has been passed down by ear through generations, and is still a popular learning method for this kind of music today. One example of a famous fiddler who does not know how to read music is Michael Cleveland. Michael is blind and has 80% hearing loss, making it impossible for him to read traditional music notation. Despite not being able to read music, he is a highly acclaimed bluegrass fiddler.

If you want to play mostly popular music, you do not necessarily need to know how to read music. A great majority of popular music is written in keys that aren't necessarily violin-friendly. Singers tend to prefer flat keys, and us violinists prefer sharps! Being able to hear a tune and play it in a key that is comfortable for you is a valuable skill to have, and one that does not require the skill of reading music. Additionally, popular music tends to use a lot of complex rhythms, which can make reading the sheet music more challenging than playing by ear. Lindsey Stirling is a world-renowned popular violinist who has said she plays mostly by ear.

However, if you want to learn how to play classical music, you do need to know how to read music. Many classical pieces, especially those in the standard violin repertoire (Sibelius, Mendelssohn, Tchaikovsky, solo Bach, etc.) are extremely complicated and include several fast passages and multiple double stops, which are virtually impossible to learn entirely by ear. I have never met a classical musician who does not know how to read music.

Your violin goals

If your goals are to play music for fun, then reading music is absolutely not a requirement.

If your goals are to play or jam with a band playing fiddle or folk music, reading music is not necessarily a requirement. A lot of that music is improvised (which means it's made up on the spot), so it does not require sheet music. However, you do need to understand scales and chords, and the circle of fifths.

Interested in learning more about music theory? Check out my music theory course:
👉https://www.learnviolinonline.org/music-theory-for-violinists

If your goals are to play in a classical ensemble, such as an orchestra or a string quartet, you do need to know how to read music. Classical ensemble music is typically extremely long, and it is quite difficult and time consuming to learn 20+ pages of music by ear. Additionally, if you're playing an inside voice (think: 2nd violin), it can be quite challenging to hear all of their notes in recordings. Finally, the majority of classical ensemble pieces include a lot of rests, regardless of the part that you're playing. Figuring out how long these are and counting them without the sheet music adds an unnecessary layer of difficulty in my opinion.

Ready to start your note reading journey? Check out my course The Basics of Note Reading:
👉https://www.learnviolinonline.org/the-basics-of-note-reading