Plain text means just that— text and nothing else. No fancy formatting, no text colors, no fonts other than the system default. These files can be considered a universal format because virtually all systems support plain text. It’s a good format to use if you’re interested in data archiving. With these four plain text editors on iOS and iPadOS, it won’t matter in which company’s ecosystem you store them.
Pretext
Pretext is a minimal editor that integrates directly with the Files app. It supports plain text and Markdown, but you can also preview and export HTML. You can change the size of the font (it uses the system font) natively, and with a US$0.99 in-app purchase you can unlock a couple of app icons and dark mode. App Store: Free (Offers In-App Purchases)
iA Writer
iA Writer gives you a minimalist space in which to write your thoughts. Start in plain text and preview in HTML. Organize documents from different clouds, embed links, pictures, tables, and other text files within plain text. It also has a feature that highlights “superfluous adjectives, weak verbs, repetitive nouns, and false conjunctions.” App Store: US$49.99
QuickText
With QuickText you can write in plain text and edit other text formats like Markdown, HTML, Tex, and more. You can adjust the font family, font size, and line-height, then sync your documents to iCloud, Dropbox, and Google Drive (OneDrive isn’t supported). There are in-app purchases to get color themes, although light and dark mode are free. App Store: Free (Offers In-App Purchases)
Editorial
Editorial is a plain text and Markdown editor with HTML preview like the other apps. What sets Editorial apart is its support for workflows and scripts for automation. You can even write Python scrips with an integrated code and UI editor. It supports snippets as well so you can quickly add bits of text to your documents like the current date. TextExpander snippets are supported, too. App Store: US$4.99
Sorry to break this out to all of you, but iA Writer is now almost 40 USD in the App Store.