# Callback does not trigger when one component as input of too many callbacks? **URL:** \ **Category:** Dash Python\ **Created:** [March 28, 2019, 10:47am UTC](https://community.plotly.com/t/callback-does-not-trigger-when-one-component-as-input-of-too-many-callbacks/21534 "2019-03-28T10:47:52Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![httr](https://avatars.discourse-cdn.com/v4/letter/h/e47774/32.png) [@httr](https://community.plotly.com/u/httr)\ **Post date:** [March 28, 2019, 10:47am UTC](https://community.plotly.com/t/callback-does-not-trigger-when-one-component-as-input-of-too-many-callbacks/21534/1 "2019-03-28T10:47:52Z")
I would like to have one radio button group acting as the input of 50ish callbacks. But if I do that, some callbacks do not trigger on change of the radio button. Reducing the number to 20, all callbacks are triggered. I guess this is similar to this post > [@Is there a limit (or limitations) on how many callbacks can be used?](https://community.plotly.com/t/is-there-a-limit-or-limitations-on-how-many-callbacks-can-be-used/10058): > > I have a multi-page app with 3 pages with 64 callbacks. The first page has 29 callbacks, the second has 19 and the third has 16. The app runs fine on localhost but when deployed to Heroku the third page hangs when loading. There are no error messages, it just seems that not all of the callbacks complete firing. If I remove some of the callbacks and deploy to Heroku then it runs fine. Further, if I add some more callbacks to the third page and try to run on localhost then the same thing happens… Is there an answer or workaround yet? ---
**Author:** ![Damian](https://avatars.discourse-cdn.com/v4/letter/d/34f0e0/32.png) [@Damian](https://community.plotly.com/u/Damian)\ **Post date:** [March 28, 2019, 1:54pm UTC](https://community.plotly.com/t/callback-does-not-trigger-when-one-component-as-input-of-too-many-callbacks/21534/2 "2019-03-28T13:54:40Z")
I’ve not experienced this issue myself, but an obvious workaround seems to be to consolidate the callbacks now that multi-output is available: [📣 Multiple outputs in Dash - Now Available!](https://community.plotly.com/t/multiple-outputs-in-dash-now-available/19437) I have some examples where I have 1 input with 12 outputs and 120 states, the performance is great. ---
**Author:** ![flyingcujo](https://avatars.discourse-cdn.com/v4/letter/f/e480ec/32.png) [@flyingcujo](https://community.plotly.com/u/flyingcujo)\ **Post date:** [March 28, 2019, 5:16pm UTC](https://community.plotly.com/t/callback-does-not-trigger-when-one-component-as-input-of-too-many-callbacks/21534/3 "2019-03-28T17:16:03Z")
I am experiencing a similar problem but on a much smaller scale. In one callback, I have the values of 2 daq.sliders as inputs. This callback get triggered (yet the output to a hidden div is not saving the return value). If I use the same 2 daq.sliders as inputs into a 2nd callback, the this 2nd callback does not get triggered. I’m currently trying to generate a test file to share that will reproduce this problem. ---
**Author:** ![flyingcujo](https://avatars.discourse-cdn.com/v4/letter/f/e480ec/32.png) [@flyingcujo](https://community.plotly.com/u/flyingcujo)\ **Post date:** [March 29, 2019, 1:12am UTC](https://community.plotly.com/t/callback-does-not-trigger-when-one-component-as-input-of-too-many-callbacks/21534/4 "2019-03-29T01:12:01Z")
In my case, solved today after my initial post, was to use Google Chrome and press F12 after performing the action in which a callback should have been triggered. Doing so showed that an unrelated compont did not have it’s value defined prior to the callback being invoked. For me, pressing F12 helped identify a problem I was having after spending several hours creating test code to help narrow the problem. F12 might be a good next step for you.