New York Times Co. is experimenting with ways to limit its exposure to online ad blocking, becoming one of the highest-profile online publishers to take such action.

On Monday morning, some visitors to the Times’ website who had ad blocking tools enabled were greeted with a message stating “The best things in life aren’t free.” To access the Times’s content, they were prompted to either purchase a subscription or “whitelist” the site to allow its ads to appear.

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