The tricky thing about suspicion is that a genuine red flag and pure anxiety feel identical from the inside. Both arrive with the same racing certainty, the same conviction that you finally see clearly. The feeling is not a reliable guide to which one you are holding, so we need better tests than intensity.
A useful first question is whether your worry points to specific, checkable behaviour or to a vague, shape-shifting dread. "They said they were at the office but their story keeps changing" is evidence you can gently examine. "I just have a feeling" that survives every reassurance, that mutates the moment one worry is answered, tends to be anxiety wearing evidence's clothing.
A second question is about history and pattern. Is this new behaviour in them, or a familiar feeling in you. Many of us carry alarms installed by earlier betrayals or childhood insecurity, and those alarms can blare in a perfectly safe room. Recognising your own tripwires is not the same as excusing a partner. It is refusing to try them for someone else's crime.
A third test is what reassurance does. When a fear is proportionate, honest reassurance settles it, at least for a while. When a fear is anxiety-driven, reassurance is a bucket poured into a well, gone in a moment, demanding another. If nothing your partner does ever quiets the worry, the problem may live more in the worry than in your partner.
If this is you, please be tender with yourself, read our trust piece, and consider that a good therapist untangles this knot faster than any surveillance ever could.
And here is the part a tracking site is oddly well placed to admit. Data does not cure paranoia. A person braced for betrayal will find menace in an innocent blue dot and reinterpret the next one too. The way out is not more information about your partner. It is a little more understanding of yourself, and the courage to ask instead of assume.