Inspect the selected display
Open Settings, System, Display, Advanced display and select the television or monitor you mean to change. Microsoft shows the current resolution and refresh rate there. Keep those values together: a display mode is a combination, not just the largest number in the refresh list.
If two screens are attached, confirm the selected name before applying a change. Otherwise the laptop may become smoother while the television continues using the original timing.
Read the options before selecting
Windows lists rates supported by the detected display route. Microsoft marks some options with an asterisk when that rate cannot use the current resolution; selecting it changes resolution as well. Read the list carefully and decide which combination serves the viewing task.
A high refresh rate can be useful for interaction, but the highest listed value is not automatically the best presentation for every source. Source frame rate, app behavior and TV processing still affect motion. Do not describe a desktop setting as creating new recorded frames.
Compare one mode at a time
Use a familiar passage containing a slow pan or moving text. Keep the source, player and television processing fixed while comparing a supported output mode. Record both resolution and rate after each change so a sharpness difference is not mistaken for a timing difference.
If the display becomes unusable, return to the prior supported configuration through the available recovery prompts. Avoid experimenting with undocumented custom timings merely to reach a marketing specification.
Separate dynamic refresh from programme matching
Windows Dynamic Refresh Rate is an activity-oriented feature with its own hardware requirements. Microsoft specifies VRR support and at least 120 Hz for DRR. Its purpose is not a promise that every film will trigger its original frame rate.
For help, supply the selected screen, mode pair and the actual symptom. “Judder on this camera pan at this mode” is more precise than “the television supports 120 Hz, so all video should be 120 fps.”
Questions answered
What does an asterisk beside a refresh rate mean?
Microsoft says that choice does not support the current resolution and will change resolution when selected.
Does a 120 Hz display make a film a 120 fps source?
No. Display refresh and source recording frame rate are different properties.
Sources & further reading
Official references for the subjects discussed. Service terms and device software can change.