Inter Font vs Sf Pro: Comparison for Mobile App Interfaces

Picking the right typeface for a mobile app sounds like a small decision. It isn't. The font you choose directly affects how fast users read content, how comfortable they feel tapping through screens, and whether your app looks polished or cheap. When designers narrow their options down to Inter and SF Pro, they're choosing between two strong contenders but the differences between them matter more than you might expect. This comparison breaks down what actually changes on screen when you swap one for the other, so you can pick the font that fits your product.

What exactly are Inter and SF Pro, and where do they come from?

Inter is an open-source sans-serif typeface designed by Rasmus Andersson, first released in 2017. It was built specifically for screens particularly user interfaces. You can grab it for free from Google Fonts or GitHub, and it ships with a wide range of weights from Thin to Black. Because it's open source, there's no licensing cost, which makes it popular with startups, indie developers, and teams that need a clean UI font without legal headaches.

SF Pro is Apple's proprietary system typeface, designed by the Apple design team. It powers every piece of text you see across iOS, iPadOS, macOS, watchOS, and tvOS. You don't need to bundle it in your app it's already on every Apple device. SF Pro comes in several variants, including SF Pro Text (for body copy), SF Pro Display (for larger headings), and SF Pro Rounded. Apple doesn't allow you to redistribute it, but you can use it freely within Apple platforms.

Both fonts belong to the geometric sans-serif family, but they were made for different contexts. Inter was designed to work everywhere. SF Pro was designed to work inside Apple's ecosystem.

How do Inter and SF Pro look different on a phone screen?

At first glance, the two fonts share a similar personality clean, neutral, modern. But spend a few minutes comparing them side by side on a mobile screen, and the differences start to show.

Inter has slightly wider letterforms, taller x-height relative to its cap height, and open apertures (the openings in letters like "c" and "e"). This gives it a friendlier, more readable feel at small sizes. Its numerals are tabular by default, which helps when you're designing dashboards, financial screens, or any layout with aligned numbers.

SF Pro is more compact. Its letterforms are tighter, with narrower spacing. Apple designed it this way because iOS interfaces pack a lot of information into small spaces think of settings screens, notification panels, and system dialogs. The compact width means more text fits on a line without shrinking the font size.

Here's a quick visual comparison:

Lowercase "a" and "g" Inter uses a single-story "a" and a simplified "g" that stay readable at tiny sizes. SF Pro defaults to a single-story "a" too but has slightly more conventional letter construction.
Punctuation and symbols Inter's punctuation marks are bolder and more visible. SF Pro's are lighter and blend into the system aesthetic.
Spacing Inter has more generous default tracking. SF Pro feels denser.

Which font handles small text and long reading better on mobile?

Readability is where this comparison gets practical. Mobile users read on small screens, often in poor lighting, while distracted. The font needs to stay legible at 14px, 13px, even 12px.

Inter holds up well at small sizes because of its tall x-height and open letter shapes. When you render body text at 14px on a standard mobile screen, Inter's characters remain distinct. The letters "l", "I", and "1" are easy to tell apart. The "0" and "O" have enough contrast to avoid confusion.

SF Pro also performs well at small sizes Apple wouldn't ship a font that doesn't but its tighter spacing can cause visual crowding on dense screens, especially for users with lower vision. Apple compensates for this by applying Dynamic Type, which adjusts spacing and weight automatically as the user changes their system font size. If your app supports Dynamic Type (and it should, if you're building for iOS), SF Pro adapts smoothly.

If you're building an app that involves long-form reading articles, notes, messages both fonts work, but Inter's wider spacing reduces eye strain over extended reading sessions. If your app is more task-oriented forms, buttons, navigation SF Pro's density is actually an advantage because it keeps UI elements compact.

Can I use Inter and SF Pro across both iOS and Android?

This is the question that usually decides the whole debate.

SF Pro is Apple-only. You cannot legally bundle it into an Android app. If your mobile product runs on both iOS and Android, you can't use SF Pro as your cross-platform typeface. On Android, SF Pro simply doesn't exist as a system font.

Inter works everywhere. You can embed it in iOS apps, Android apps, web views, desktop applications anywhere you can load a custom font. This makes it the more practical choice for teams that maintain a single design system across multiple platforms.

Some teams use a hybrid approach: SF Pro on iOS (since it's the native system font and feels "at home") and Inter on Android and the web. This creates a subtle visual difference between platforms, but both fonts are neutral enough that most users won't notice. If consistency across every screen matters to your brand, go with Inter everywhere.

If you're exploring other options beyond these two, there are several strong alternatives to Inter worth considering depending on your project needs.

What about licensing and cost?

This is where the two fonts diverge completely.

Inter is released under the SIL Open Font License. You can use it for free in personal and commercial projects, modify it, redistribute it, and bundle it in apps without paying anything. There are no restrictions on platforms or usage types.

SF Pro is free to use on Apple platforms, but Apple's license restricts you from redistributing the font files. You cannot include SF Pro in an Android APK, a web font kit, or a design tool download. If you try to bundle SF Pro into a non-Apple product, you're violating the license.

For budget-conscious teams or open-source projects, Inter removes the licensing question entirely. If you're building exclusively for Apple's ecosystem, SF Pro's license is generous enough you just need to reference it as the system font rather than shipping it yourself.

What mistakes do designers make when choosing between these fonts?

Several common errors come up repeatedly:

Ignoring platform context. Choosing SF Pro for an Android app or forcing Inter onto an iOS app when the rest of the system UI uses SF Pro creates a visual disconnect. Users notice when text looks "slightly off" even if they can't articulate why.
Not testing at small sizes. Fonts look great in Figma at 24px. They need to work at 13px and 14px on actual devices. Always test body text on a real phone before committing.
Skipping Dynamic Type support. On iOS, users can set their preferred text size system-wide. If you hard-code Inter's sizes and ignore Dynamic Type, you're breaking accessibility for a significant portion of users.
Pairing with mismatched weights. Inter's Regular (400) weight is slightly lighter than SF Pro's Regular. If you swap one for the other without adjusting weights, the visual hierarchy shifts.
Overlooking font file size. Inter's full variable font file is around 300KB. If you're only using two weights, subset the font to reduce load time. SF Pro doesn't have this concern on Apple devices since it's pre-installed.

Designers who want more flexibility in their font stack might also look into open-source font replacements for Inter on Google Fonts, which can offer similar aesthetics with different technical trade-offs.

So which font should I actually use for my mobile app?

There's no universal winner. The right answer depends on your situation:

Building for iOS only? Use SF Pro. It's native, it respects user preferences automatically, and it matches the rest of the operating system.
Building for Android only? Use Inter. SF Pro isn't available on Android, so Inter gives you a clean, professional alternative.
Building for both platforms? Use Inter everywhere for visual consistency, or use SF Pro on iOS and Inter on Android for a platform-native feel.
Building a web app or progressive web app? Inter is the clear choice. It loads from Google Fonts with a single line of CSS and renders well in every browser.
Working with a tight budget? Inter is free and open source with no licensing restrictions.

Both fonts are well-designed and widely trusted. The decision usually comes down to platform requirements, cross-platform consistency, and licensing constraints rather than one font being "better" than the other.

Quick checklist before you finalize your font choice

✅ List every platform your app targets (iOS, Android, web, desktop)
✅ Check licensing restrictions for each platform
✅ Test body text at 13px and 14px on a real device not just in your design tool
✅ Verify that your chosen font supports all the languages and scripts your app needs
✅ Confirm Dynamic Type (iOS) or system font scaling (Android) works correctly with your font
✅ Compare your font weight choices across both options to keep hierarchy consistent
✅ Subset your font files to include only the characters and weights you actually use
✅ Get feedback from real users on readability before shipping

Start by testing both fonts in a prototype on actual devices. Five minutes of real-device testing tells you more than an hour of staring at a desktop mockup.

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