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What does open rate tell you

There has been an lot written about open rates in the past, but there are two posts that stand out to me. One was the EEC’s post on renaming open rate to render rate and Mark Brownlow’s excellent post on what open rate does and does not measure. I’ve also weighed in on the subject. The issue is still very confused.
If asked, most people will tell you that open rate is the number of emails that were opened by the recipient. The problem is that this isn’t actually true. Open rate is measured by the number of people that display an image in an email. Traditionally this has been a uniquely tagged 1×1 pixel, until some filters and mail clients stopped displaying 1×1 pixels. More recently, every image in an email is tagged, so opening one image would record as an open.
So open rate doesn’t actually tell a sender how many people opened and read an email. It really only records that an image in a particular email is loaded. It does not record when an email is opened. Some people don’t load images by default. Some people don’t load images at all, even when they open and actively read the text portion of the email.
Clearly, there are some uses for open rates. It can give a useful metric when comparing different forms of the same email (A/B testing) and when looking at user engagement over time. However, we have also recently seen that open rate is not predictive for click through rate.

8 comments

  1. Matt Blumberg says

    I’ve also thought that comparing open rates over time is useful. The relative rates on one campaign vs. another are probably indicative of usage patterns, even if the nominal rates aren’t reliable.

  2. Justin Coffey says

    The other big use of the open rate (when looked at over time as Matt suggests) is to find out if a campaign or client in particular is hitting the junk folder. It’s a bit of fuzzy math, but this is what I use to determine junk folder hits at Hotmail:
    If the open rate is less than 5% this is a red alert, especially as it passes below the 3% mark.
    For sure, the campaign in particular could just be completely uninteresting, but when combined with two other stats (again at Hotmail) you get some useful information:
    What is the click to open rate? If it is very high, say 50%, then you can say for sure that your mail ended up in the junkfolder and those reads are from the users who actually hunted the campaign down in their junkfolder.
    What is the complaint to open rate? This is less scientific, but if you have one complaint (or more) for every 10 opens then perhaps your campaign initially started in the inbox, but then the remainder got sent to the junkfolder as the first recipients reported it as spam in high numbers.
    Like I said, this is not an exact science, but these sorts of ways of looking at data can give you a smidge more insight.
    Hope that helps :).

  3. Dave Nelson says

    I’ve considered adding my “clickers” to my “openers” pool – only those that didn’t show up in the opens, of course. I recently did a survey where 800 people responded, but 200 of those did not show up on the open report. Partly because there were no images that they needed to see before proceeding to the survey.
    And @Justin, good tip on the click to open rate.

  4. Justin Coffey says

    @Dave, you should read up on the EEC’s SAME proposal for standardization of reporting. It talks about adding clicks to opens in the case of missing opens (it also changes nomenclature to call an open a render), but yes, we do that :).

  5. laura says

    Actually Justin, S.A.M.E defines “open” as either an image load or a click. A “render” is simply an image load.

  6. Justin Coffey says

    ah, thanks for that clarification Laura :).

  7. The Proverbial Barry says

    open rate means nothing to isps but spammers er i mean marketers keep asking me about it anyway
    why do they think i care?? i tell my usrs to leave images off, its safer

  8. Andy says

    I’v just got round this one. I’ve seen ESPs, including mine, also registering an open when someone clicks a tracked link when images are not loaded, as well as registering the click. The logic is that because someone has clicked the link, you know the email has been opened.
    In plain text only emails for instance if no-one opts out, you could have the same number of opens as unique recipient clicks.
    Obviously lately the EEC would like to have a render rate for image loads, a click through rate for click throughs and then I would presume and amalgamated open rate based on the relative combination of the two.
    The next question is, which clicks are relevant for the click through, ie: clicking the browser view link – is that a click through or just an open? seeing as it has not completed the call(s) to action of the email and therefore could skew the email’s results if included in the clicks for the campaign?

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