What is the best SSH client app for iOS?
Stability and security are the main issues.
It could be paid or free.
Easy to use is not important.
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Sign up to join this communityPrompt 2 by Panic is one of the best SSH clients for iOS and has a nice UI, a bit expensive though.
With regard to security, you can add and even generate SSH keys directly in Prompt. From the Prompt page on Panic's website:
You can also PIN lock Prompt so that it remains secure even if your device is unlocked. And yes, you can also lock Prompt with Touch ID.
WebSSH is okay.
It has all the features you'd expect from an SSH client, the UI doesn't feel very polished though and I have a feeling the actual terminal is a JS app; it's kinda slow when the screen refreshes frequently (top/airodump-ng/etc).
Give it a try, if you're an occasional user it'll be fine, otherwise invest in Prompt 2.