4 ms·

No, it only caches when they are requested by the user - google acts more like a proxy. Essentially they're preventing the remote server from grabbing HTTP head

No, it only caches when they are requested by the user - google acts more like a proxy. Essentially they're preventing the remote server from grabbing HTTP headers/cookies from gmail users but not preventing them from tracking when it is loaded, chronologically.

chatmasta 9y ago
The google servers download every image, regardless of whether or not the user later opens it or not. So since every image is downloaded, and subsequent downloads come from google cache, the pixel becomes an ineffective way of tracking open rate.
- viraptor 9y ago
  You can only get the image from cache if it's the same URL. You can still vary those between recipients.
  - chatmasta 9y ago
    But if it's a different URL for each recipient then google will fetch each individual URL, for each email. So every URL will be opened exactly once, by the google fetch that happens when the google server receives the email. The user will fetch the pixel from google cache. So how can you track open rates by pixel download when 100% of pixels are downloaded just one time? It probably depends on email clients. If a desktop client fetches email direct from smtp then it will probably also fetch the pixel directly. So tracking all downloads after the first (by google) may yield some signal, albeit not for gmail web users.
    - jaggederest 9y ago
      Try it. The various MSPs I use report to within a minute whether I open an email or not, and they do this effectively on Gmail and other clients as well. I see no way they could do this besides the tracking pixels they embed in email, which means that google does not prefetch, but I'd be happy to be proven wrong.
    - viraptor 9y ago
      Are you sure they download when Gmail receives the email? I'm pretty sure it's on first use.
- jaggederest 9y ago
  This is factually incorrect. At least for the MSPs I use, they report the open time accurate to within a minute whether I'm using Gmail or not. I see no way for them to do this besides tracking pixels embedded in the document, since I don't see any other outside resources.

chatmasta 9y ago

The google servers download every image, regardless of whether or not the user later opens it or not. So since every image is downloaded, and subsequent downloads come from google cache, the pixel becomes an ineffective way of tracking open rate.

viraptor 9y ago
You can only get the image from cache if it's the same URL. You can still vary those between recipients.
- chatmasta 9y ago
  But if it's a different URL for each recipient then google will fetch each individual URL, for each email. So every URL will be opened exactly once, by the google fetch that happens when the google server receives the email. The user will fetch the pixel from google cache. So how can you track open rates by pixel download when 100% of pixels are downloaded just one time? It probably depends on email clients. If a desktop client fetches email direct from smtp then it will probably also fetch the pixel directly. So tracking all downloads after the first (by google) may yield some signal, albeit not for gmail web users.
  - jaggederest 9y ago
    Try it. The various MSPs I use report to within a minute whether I open an email or not, and they do this effectively on Gmail and other clients as well. I see no way they could do this besides the tracking pixels they embed in email, which means that google does not prefetch, but I'd be happy to be proven wrong.
  - viraptor 9y ago
    Are you sure they download when Gmail receives the email? I'm pretty sure it's on first use.
jaggederest 9y ago
This is factually incorrect. At least for the MSPs I use, they report the open time accurate to within a minute whether I'm using Gmail or not. I see no way for them to do this besides tracking pixels embedded in the document, since I don't see any other outside resources.