Always write a cover letter from scratch. It's better to invest time in five most relevant positions and apply with a complementing cover letter (and resume), than to apply for fifty positions without any background research (AKA generic cover letter/resume.)
If you are applying online to a big tech company, it almost always goes into an Applicant Tracking System (ATS). The ATS scans your resume and cover letter for keywords, and matches it with the keywords in the job description or specific keywords as asked my the hiring manager. (You can get through ATS just by copy-pasting the job description in your cover letter. Don't do it). Once you pass through the ATS filter, the recruiter don't seem to care much about the content of your cover letter, but it makes a huge difference when it goes to the hiring manager.
Apart from convincing why you are a perfect fit for the role, share interesting stuff about you like a link to your website (highly recommend this for new grads in tech roles), github profile, previous internship experiences and what excites you about this role.
PS - The most effective way to get a call is to network.(and avoid the whole ATS blackhole).
+10 on the networking. Use LinkedIn, leverage any/all connections. Reach out to people, let them know you are looking.
+1 on the ATS. They are a waste of your time, generally. If you see an interesting position, try to find an "in" to the company via your network, 1st or 2nd order. See if you can reach the hiring manager directly. HR/ATS get in the way of that. They are supposed to be a service, but as often as not, they are a bottleneck of dubious value. Think of this as engineering your way around the bottlenecks.
+1 on writing a personalized cover letter for each application (e.g. resume submission). I spent quite a bit of time reading/listening to what people thought were good cover letters. What it comes down to is, be real, be yourself. Explain what excites you and how this position does this.
After I did all of this, I found myself a) applying to fewer positions (this was early this year), and b) getting a far higher response rate (60+%). This culminated in multiple interesting offers.
YMMV, but good cover letters help you stand out. Show you are a human being that they want on their team.
Didn't even think of the ATS angle. Yikes, so if a cover letter doesn't have enough related keywords it might not even make it past machine filters? That makes me even more anxious - most postings, actually virtually every posting I see, the overlap btw required skills posted and my skills is rarely more than 50% or 60%.
Sucks for dyslexics even high performing dyslexics like myself find writing cover letters hard and I would only do that for some very specific and life changing jobs - some run of the mill startup not so much.
If you are applying online to a big tech company, it almost always goes into an Applicant Tracking System (ATS). The ATS scans your resume and cover letter for keywords, and matches it with the keywords in the job description or specific keywords as asked my the hiring manager. (You can get through ATS just by copy-pasting the job description in your cover letter. Don't do it). Once you pass through the ATS filter, the recruiter don't seem to care much about the content of your cover letter, but it makes a huge difference when it goes to the hiring manager.
Apart from convincing why you are a perfect fit for the role, share interesting stuff about you like a link to your website (highly recommend this for new grads in tech roles), github profile, previous internship experiences and what excites you about this role.
PS - The most effective way to get a call is to network.(and avoid the whole ATS blackhole).