411 - LengthRequired


I get a 411 - LengthRequired in the IIS logs coming thru unbounce for the webhook.

I am able to make a successful request if I go to the webhook directly thru the browser url…

Any ideas?


Hey Austin - are you still experiencing issues here? I double checked and see that Johnny’s replied several times to your support ticket but there’s always the possibility that the replies aren’t getting to you.

The 411 (Length Required) error would be returned by your servers. It seems that when your server receives the WebHook data, it’s not happy with the format.

I found this post at http://robertgreiner.com/2013/01/the-… that addresses the issue though I’m not certain it’d solve the issue you’ve seen.

Let me know if that helps or if you have any follow up questions… hopefully we can find a solution for you.


This is a change that unbounce will need to make in their code as they are the ones making the request. I’ve already pointed this out in previous tickets and/or chats. Our webhook(s) all work in browsers, fiddler, and in other .net code posting to them. Unbounce, however, does not work because it is not setting the contentlength or it is not setting it correctly.

Let us know when this is addressed.


Hi Austin, really sorry you’re running into issues with this. I just confirmed that we are indeed setting the Content-Length header (here’s a screenshot of the test post I did using RequestBin:

If we’re getting an error response from you, we should also show that on our side when you look under “View Leads”. Are you seeing error indications on our side as well, or just in your logs?


Been using unbounce for years. Have been using the webhook feature the whole time without issue and have not made any changes to the script that receives the leads in over a year.

I had to perform my own network capture to show that our server was not returning the 411 error. The script returns a 301 redirect to a thank you page. Unbounce system is logging that as an HTTP 411 error in their web console. This is a new error created in the last few days.

Support repeatedly brushed the issue off and pointed the finger at me. I hope this information may be helpful to other unbounce users who may run into this problem. The culprit this time is some change to their system made it incapable of handling a 301 redirect response. This is unlikely to be the same root cause as Austin’s issue since he had the problem a year ago and their system has been gladly accepting redirects that whole time from me.


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