Want to know how to take screenshot on Snapchat without them knowing, then read the post given here. You can try any of the following steps.
1. Clicking a picture, from another device.
2. Mirroring app feature.
3. By asking Google Assistant.
4. Screen recording.
5. Using apps like Private Screenshots.
6. Snapchat desktop version.
7. Use third-party apps or enable airplane mode.