I like Google flights for generally tracking flight prices, but it comes with caveats.

Google flights often gives you the "lowest price" for a flight you would never book. For example, an itinerary on two different airlines that requires the purchase of separate tickets.

The "lowest price" is almost always the flights that do not come with seat assignments, and sometimes no bag allowance (think the United basic economy fare). So when you actually go to purchase the ticket, it may be $50-$100 more expensive.

With that said, it is good for identifying drops in fare, and usually the airlines drop their prices at the same time. I was watching a fare recently, and when it dropped, I went and checked prices on Southwest. SW actually had the best price AND the best flight options, so I bought that flight. Since you can't set up a fare alert for that airline, Google flights is a decent way to be alerted when to check prices (vs checking every day).

The Google flight calendar is also good for generally seeing what months/weeks have the lowest prices to a certain destination you may be interested in (assuming travel dates are flexible).