Pesky blue border below header in all Mobile apps

Hi, I am trying to figure out why there is a blue border below the header of every Mobile app. None of the components or themes are set to have a blue color, yet it still appears. I even tried with a fresh new app and it's there by default.

Any ideas? Thanks.

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Just following up on this, because I am making a lot of functional mockups right now in Retool Mobile to show off app ideas and I hesitate to show them off to decision makers because that blue top border looks like an oversight.

Can we please have an option to control its visibility, color and/or thickness?

Thank you.

Hey @27shutterclicks! Definitely strange—I'm not seeing the same blue header on my end. Do you know if you have any global CSS set under your Settings > Advanced ? Preloaded CSS field? Also, if it's alright with you, I'd be happy to step into your app and poke around to see if I can find the source of this mysterious blue border!

Hi @victoria, I don't have any preloaded CSS configured in Settings > Advanced.

I've also seen this blue border in screenshots other users have posted lately in the forums.

Yes, please feel free to look into my app and see if you can fix it.


Oh, that's super helpful. I looked at a few other examples and it seems like this blue line is related to the new Runtime (blue line means new Runtime). You can click on the Runtime section in the bottom of your apps to remove the blue line.

I filed this with the Mobile team to see how we can remove the blue line, I definitely understand not wanting it to show up in your apps! Thank you for surfacing this :pray:

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Good news! The mobile team is planning to remove it this week, which means it should be gone by next week’s Cloud release. We will instead add a red line for the legacy runtime to indicate that an upgrade is recommended.

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I suspected it may have to do with the runtime, but didn't actually try to switch back to the legacy one.

What exactly are the differences between the legacy and the new runtime?

What happens if I downgrade to the legacy runtime? Will I lose any features of the upgraded runtime?


Functionally, the only difference is that the new runtime is faster. It shouldn't have any other affects otherwise and you should be able to downgrade/upgrade without introducing any breaking changes. There can always be edge cases, though, so definitely let us know if you hit any snags when downgrading/upgrading and we'll make sure to get you back to a working state!

I downgraded the runtime and it did get rid of the blue border. But everything is painfully slow now compared to the upgraded runtime, so I look forward to the fix you mentioned.


Ack, I'm sorry about this happening. I'll keep you updated on the change!

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I was looking forward to the removal of the blue line in this week's update, but I don't see any changes so far, or any mentions in the change log.

Has it been overlooked? :slight_smile:

Checking :eyes:

It'll be out in this week's release! Targeting end of week :slight_smile: Thank you for all your patience here.

Thank you, I'll be waiting :slight_smile:

@27shutterclicks should be gone now!

:open_mouth: I still see it on my end. Here's a fresh screenshot. App is running the latest runtime.

I can confirm as well - still seems to appear.

:eyes: looking into this!

Looks like the blue border is gone now as of this week. Thank you all for making it happen, it's such a relief :slight_smile: :raised_hand:

Glad to hear it! Thank you for your feedback and all your patience here :slight_smile:

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