As time advanced, so did digital technology. And volume of online PR activities also became more popular because of being both cost and time efficient. But like conventional PR activities, the effectiveness of online PR activities also need to be investigated.

The Public Relations Society of America (PRSA), a pioneer organization in this arena that has been developing PR strategies since 1947, prescribed 5 steps to measure online PR effectiveness:

1. Engagement: The number of people who got themselves engaged with an item (can be measured by social media shares, likes and comments). In other words, how many people are engaged with your brand.
2. Impressions: The actual number of people who really viewed an item. That is, how many people actually took interest in your brand.
3. Items: Any potential content (e.g. social media or blog posts, articles) that originally appeared as a digital item on a digital media. In easy words, how dominant or visible your brand is online.
4. Mentions: How many online items mention the particular brand, organization, or product. In others words, how frequently your brand is being mentioned (through shares, likes, comments, or recommendations etc.)
5. Reach: How far the PR campaign managed to penetrate overall (in terms of the number of clients reached). Or, how many people your brand has reached to.

Reference
Yann, Arthur. PR Measurement Standardization: Moving Toward Industry Agreement: PRSA.