Recently, my friend was talking about some output he got from running the minikub program. Each line included a leading emoji character. He was not thrilled, and I don’t think they did it well. But when used appropriately, emoji can add valuable context to the output.

root@test# minikube start
? minikube v1.0.0 on linux (amd64)
? Downloading Kubernetes v1.14.0 images in the background ...
? Tip: Use 'minikube start -p <name>' to create a new cluster, or 'minikube delete' to delete this one.

? Unable to start VM: Error getting state for host: getting connection: looking up domain: virError(Code=42, Domain=10, Message='Domain not found: no domain with matching name 'minikube'')

? Sorry that minikube crashed. If this was unexpected, we would love to hear from you:
? https://github.com/kubernetes/minikube/issues/new
root@test# minikube delete
? Deleting "minikube" from kvm2 ...
? The "minikube" cluster has been deleted

I should say, in the interests of full disclosure, that I have written tools that include unhelpful emoji in the output. Some of the emoji are not helpful. The crying cat because it crashed? Doesn’t add anything. The broken heart when the cluster is deleted? I don’t have time for your guilt trips. But the light bulb for a tip and the bomb for a Big Bad Error help draw attention to what could be a wall of text.

Here’s what I see as some guiding ideas for using emoji in output:

• Have a fallback, but not a stupid one. For the code above, there’s a fallback to ASCII. If you thought the emoji added no value, check out how un-valuable the fallback is. The fallback should probably be “print nothing and go straight to the text output”.
• Don’t print emoji to logs. The console should be human-readable (and a well-placed emoji can help with drawing attention to the right places), but logs should be machine-readable (well, grep-readable). Log messages should be more structured anyway, so maybe it doesn’t really matter, but don’t rely on your user having an emoji keyboard available when they need to grep the logs.
• Try to use unambiguous emoji. Pictograms are language-independent, which is nice, but if you’ve ever tried to communicate with A Youth via emoji, you know there’s a lot of room for nuance. Stick to well-understood characters and document them somewhere.
• Use emoji to enhance context, not to replace text. Log parsing and screen readers are two reasons that you don’t want to get rid of text in favor of emoji. Use the emoji to draw attention to important messages and provide hints as to why they’re important, but make sure the messages still stand on their own.