# x-dynatrace header max length **URL:** \ **Category:** Open Q&A\ **Tags:** request-attributes\ **Created:** [November 28, 2022, 1:50pm UTC](https://community.dynatrace.com/t/x-dynatrace-header-max-length/37478 "2022-11-28T13:50:37Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![Romanenkov\_Al3x](https://dub1.discourse-cdn.com/dynatrace/user_avatar/community.dynatrace.com/romanenkov_al3x/32/36257_2.png) [@Romanenkov\_Al3x](https://community.dynatrace.com/u/Romanenkov_Al3x)\ **Post date:** [November 28, 2022, 1:50pm UTC](https://community.dynatrace.com/t/x-dynatrace-header-max-length/37478/1 "2022-11-28T13:50:37Z")
Hello. Can anybody tell me - max length of **x-dynatrace** header. Customer setting up firewall rules, so they need max length all request headers to allow application work, otherwise requests are blocked. Thanks. Alex ---
**Author:** ![hannahmac](https://avatars.discourse-cdn.com/v4/letter/h/dec6dc/32.png) [@hannahmac](https://community.dynatrace.com/u/hannahmac)\ **Post date:** [November 28, 2022, 1:59pm UTC](https://community.dynatrace.com/t/x-dynatrace-header-max-length/37478/2 "2022-11-28T13:59:18Z")
I don’t believe there is a size limit from a Dynatrace perspective. Typically, the HTTP header size limit is dependent on the server. (Apache, Nginx, IIS, Tomcat) ---
**Author:** ![Romanenkov\_Al3x](https://dub1.discourse-cdn.com/dynatrace/user_avatar/community.dynatrace.com/romanenkov_al3x/32/36257_2.png) [@Romanenkov\_Al3x](https://community.dynatrace.com/u/Romanenkov_Al3x)\ **Post date:** [November 28, 2022, 2:19pm UTC](https://community.dynatrace.com/t/x-dynatrace-header-max-length/37478/3 "2022-11-28T14:19:35Z")
I need value from Dynatrace. Expected answer - for example 200 symbols. Look like this: ```markup FW4;-712055999;35;-1057699572;862004;0;1310537445;1367;c15c;2h01;3hc0f4c90c;4h0d2734;6h6765016c4c42ea4085044906606ef4e6;7hc487f83ef5f244e3 ``` This header added by Dynatrace. Only Dynatrace can know it. The question is not about web server settings. Thanks, Alex ---
**Author:** ![harald\_berger](https://dub1.discourse-cdn.com/dynatrace/user_avatar/community.dynatrace.com/harald_berger/32/31754_2.png) [@harald\_berger](https://community.dynatrace.com/u/harald_berger)\ **Post date:** [November 29, 2022, 6:46am UTC](https://community.dynatrace.com/t/x-dynatrace-header-max-length/37478/4 "2022-11-29T06:46:11Z")
Hi, Unfortunately the header length is not fixed. Depending on the situation encoded binary info will be added to header. Harry ---
**Author:** ![Romanenkov\_Al3x](https://dub1.discourse-cdn.com/dynatrace/user_avatar/community.dynatrace.com/romanenkov_al3x/32/36257_2.png) [@Romanenkov\_Al3x](https://community.dynatrace.com/u/Romanenkov_Al3x)\ **Post date:** [November 30, 2022, 9:58am UTC](https://community.dynatrace.com/t/x-dynatrace-header-max-length/37478/5 "2022-11-30T09:58:37Z")
Thanks for fast response. ---
**Author:** ![Rene](https://avatars.discourse-cdn.com/v4/letter/r/7cd45c/32.png) [@Rene](https://community.dynatrace.com/u/Rene)\ **Post date:** [April 3, 2025, 8:15am UTC](https://community.dynatrace.com/t/x-dynatrace-header-max-length/37478/6 "2025-04-03T08:15:30Z")
[@harald\_berger](https://community.dynatrace.com/user/760) Hello Harald, We use Dynatrace for mainframe Cobol under CICS and have used a TAG buffer length of 100 bytes for the stubs based on the examples in your documentation. [assets.dynatrace.com/global/doc/appmon/integrations-and-extensions/development-kits/agent-development-kit-adk/cics-and-ims-adk/adkcobol.txt](https://assets.dynatrace.com/global/doc/appmon/integrations-and-extensions/development-kits/agent-development-kit-adk/cics-and-ims-adk/adkcobol.txt) Now it has turned out that the length can also be greater than 100 bytes and we are having problems processing it correctly. We know that the length is not fixed. In our tests, with different applications, we see lengths of 74 bytes, 85 bytes, 142 bytes. What length would you recommend so that we can most likely cover all possible cases in the future? Thanks BR; Rene ---
**Author:** ![harald\_berger](https://dub1.discourse-cdn.com/dynatrace/user_avatar/community.dynatrace.com/harald_berger/32/31754_2.png) [@harald\_berger](https://community.dynatrace.com/u/harald_berger)\ **Post date:** [April 3, 2025, 8:53am UTC](https://community.dynatrace.com/t/x-dynatrace-header-max-length/37478/7 "2025-04-03T08:53:44Z")
Hi Rene, 170 characters should be sufficient, if no custom tags are propagated. Harry ---
**Author:** ![Patrick\_H](https://dub1.discourse-cdn.com/dynatrace/user_avatar/community.dynatrace.com/patrick_h/32/37540_2.png) [@Patrick\_H](https://community.dynatrace.com/u/Patrick_H)\ **Post date:** [April 3, 2025, 9:25am UTC](https://community.dynatrace.com/t/x-dynatrace-header-max-length/37478/8 "2025-04-03T09:25:29Z")
The x-dynatrace header can contain different content as it is used for e.g. web RUM and mobile RUM - see [Infrastructure pass-through requirements for RUM Classic — Dynatrace Docs](https://docs.dynatrace.com/docs/shortlink/rum-firewall) For mobile RUM the header content can vary in length, but is just calculated it and a max size of 150 chars for the header value (excluding x-dynatrace: name) should be save. I can’t speak for web RUM here where this header is set on OneAgent - so you probably will need a solution using biggest possible value for all scenarios.