Depends on what you want to output. Webapps? Nothing, it already has all you need, especially if you are willing to use a remote server that you are ssh'ed into but you don't NEED that. For native compiled code and apps? Apple needs to release a Xcode compiler and a developer mode that lets you run self-signed binaries on the hardware.

Is there an inspector in Safari for iOS? Can I dig into the markup on a page and debug CSS and layout issues?

I do this today on my 6th gen iPad. I use MOSH, a BlueTooth mechanical keyboard, and Blink as my client. It works well.

If you develop anything for the web, don't you need to check how it renders on other browsers?

I don't do a ton of web front end work and what front end work I do is pretty simple. I'm 99% a native mobile developer and IoT C++/Python developer. Usually mobile safari is good enough for me.

Safari is usually good enough for what I do. I can use BrowserStack if need be, too.

Tangential, but it's worth noting that if what you are looking for is a portable development machine with tablet-like capatibilities, the Microsoft Surface series is arguably a better choice.

Or Google Pixelbook, if you prefer Linux over Windows.

You can program on an iPad already using interpreted languages such as Python and Lua. And you can SSH into other machines, run Git, and have a text editor already.

The main issue with developing on an iPad is that it’s not easy to load unsigned, compiled code on it, and even if you do, there’s not much that the code can do because of the system sandbox.

I would have thought the main issue would be screen size. Don't developers like large screen real estate, being able to see documents side by side, or the code of your app, a browser rendering it and the debug tools inside the browser, and stackoverflow on the side?

It depends, mostly on preference, but also eyesight (and therefore, age).

My main dev machine is a 12” MBP. I have external monitors, but do quite a bit of work even on my 9.6” iPad. I spend 9% of my time in a terminal anyhow, and have good eyesight.

The parent comment asked to put aside hardware issues, so I left this out.

I've been looking into this as well. Here's some notes: https://www.notion.so/csytan/iPad-as-a-Development-Device-99...

The main issue in my opinion is the lack of mouse support. Not saying the OS needs to support mice throughout the UI but it would be great to be able to use one just with a remote desktop app, for instance.

You could use something like codeanywhere.com though from my experience we're still X years away from running IDEs in the cloud seamlessly

Depending on your environment you may be able to do it now. The rise of cloud coding platforms means that coding on an iPad is pretty useable as long as your deployment process works with it.