Both are free. Only one writes the sentence.
People ask for a WhatsApp alternative the way they ask for a Spotify alternative: they want the same job without the company attached.
Signal’s official cost page, today: “Signal is free to use and there are no ads, no affiliate marketers, and no tracking in Signal.” It is an independent nonprofit, funded by grants and donations. Registration needs an SMS or call. After that it uses mobile data or Wi‑Fi, which your carrier may charge for. Signal does not charge for the app.
WhatsApp is also free to install and message. I am not going to invent a WhatsApp subscription. Meta’s business is not “charge you ₦500 a month for chat.” The comparison is who sees the graph of who you talk to, and whether the app is funded by ads. Signal puts that in writing. I am not going to paraphrase WhatsApp’s privacy policy from memory.
What Signal is not
It is not a drop-in status-and-channels clone. If your family lives in WhatsApp groups, broadcast lists and business catalogues, Signal will feel empty until they move. Official support even has a page titled “Does my contact need Signal?” — both sides need the app.
It is not a second phone number product. You register with a number. Your carrier may bill the registration SMS.
It is not a money app. There is no official “Signal pays you” angle. This is a tech page, not a Make Money listing.
How I would choose, labelled as opinion
If I need one private thread with a person who will install another app, I would use Signal.
If the group is already on WhatsApp and will not move, I would stay there and stop pretending a blog post migrates a family.
I would not install a “WhatsApp Plus” APK. That is how you donate the chat.
I have not audited Signal’s protocol for this page. “No tracking” is their published claim. Open their cost page if that sentence is why you are switching.