Check the user reviews—carefully

User reviews are typically the first place to check an app’s trustworthiness, especially on mobile, but treat them with caution—they’re not all that difficult to fake. Look for reviews that are a decent length, that appear to have a genuine person attached to them, and that don’t read as if they’ve been auto-generated by a bot.
Even when reviews are real, watch out for bias: Users are more likely to take the effort to report a problem with an app rather than general satisfaction with it. If there are complaints and low ratings, see what the specific problems are—and check if the developer has responded and been helpful.
It’s more difficult with desktop apps you get from the web—they may have “user testimonies” on their site, but it’s hard to know if they’re genuine too. Look for mentions of the app on places like Reddit or Twitter, or search for reviews in the press or on independent ranking portals such as Trustpilot.