Measuring the half-life of your links

Understanding the concept of the “half-life” of different types of online links is important.

“Half-life” a term most often associated with measuring radioactive decay where it helps describe:

“the period of time is takes for the amount of a substance undergoing decay to decrease by half.”

(source: Wikipedia)

In digital marketing terms the ‘substance’ we’re interested in measuring is usually impressions or clicks.

And the half-life of an advert helps describe how long it takes for the ad to receive half of the engagement it will ever get.

In the pre-digital era, the half life of, say, a TV advert used to be roughly half the duration of the paid ad campaign. Because we were buying share of voice, we could control the half-life and set it to a point where our presence in the marketplace would be at its peak.

Things are different online though, where the impact of a new message is at its highest when the content is new and fresh, and quickly dissipates to (close to) nothing, sometimes in a matter of hours.

According to data from

  • A link shared on Twitter has a half-life of 2.8 hours
  • A link shared on Facebook has a slightly longer half-life of 3.2 hours
  • A link shared through email or IM has a half-life of 3.4 hours
  • A link shared through YouTube has a half-life of 7.4 hours
  • A link shared on StumbleUpon has a half life of around 400 hours (because StumbleUpon will automatically recycle content until it has achieved the desired viewing levels if part of a paid ad campaign, or until the content is no longer receiving positive feedback from its viewers if part of an unpaid activity.)

Bitly chart showing half-life of different types of links

How to measure the half-life of your links?

You can easily measure the half-life of any link you share. At the simplest level, using a URL shortening service like gives you access to analytics data reported by the hour so you can quickly see how many hits you get and when. You’ll need to do some number juggling to calculate the half life but in most instances a quick glance at the last 24 hours chart should be enough to tell you roughly when the half-life was reached. The big downside of this manual approach is you have to move fast. Without customised tools, the free Analytics site only reports data for the last 24 hours, so if you shared your link last week it could be impossible to gauge the half-life accurately.

And remember, you can only truly measure half-life when all clicks have been received, which is, in theory, at a point in the infinite future. You need to make a call when clicks have dwindled sufficiently for you to ignore all future clicks (the long tail) and make your calculations. To help decide when is the right time to make this call, take a look at long-term clicks for a link shared a few months ago. In most instances, engagement will have  dried up after a few days in which case it’s fine to calculate the half-life from that point in time.

But how does this knowledge help you?

By knowing the relative half-life of content shared on different platforms you can determine how frequently to post to those channels or when to post (and repost) to achieve maximum impact. This knowledge can also help inform your paid advertising plans helping you align them with activity happening across social channels to achieve maximum impact.

Let me know how you get on calculating your links’ half-life levels or contact me with any questions. I’d love to hear how you get on.