What Are Icons and How Do You Choose the Right Ones for an App or Interface?
An icon is a small, simplified graphic that stands in for an action, object, or idea inside a user interface. You choose the right ones by matching style to context, then checking four things before you commit: consistency, scalability, licensing, and platform conventions. This applies whether you are picking a ready-made set for a mobile app or commissioning custom work for a brand.
What an icon is — and what it is not
An icon is functional first. It has to be recognized at a glance, often at 16–24 pixels, and it usually sits next to or inside a control the user can tap or click.
| Element | Purpose | Example |
|---|---|---|
| Icon | Represent an action, object, or state in a UI | A trash can for "delete" |
| Logo | Identify a brand or organization | A company wordmark |
| Illustration | Explain, decorate, or set tone | An onboarding scene |
| Symbol | Carry meaning beyond one product | A checkmark for "done" |
The overlap is real — a logo can be used as an app icon — but the jobs differ. A logo needs to be distinctive; a UI icon needs to be instantly legible, even when it is one of twenty on screen.
Common icon styles and where each works
- Outline (line) icons — thin strokes, open shapes. Good for secondary actions, dense toolbars, and interfaces that need a light, modern feel. They can lose clarity at very small sizes if strokes get too thin.
- Filled (solid) icons — closed shapes with solid mass. Strong at small sizes and for primary navigation, like a bottom tab bar. Mixing filled and outline in the same row usually reads as a state change (selected vs. unselected), so use that deliberately.
- Flat icons — no gradients, shadows, or depth. Fast to render and easy to keep consistent across a large set.
- Skeuomorphic icons — textured, dimensional, imitating real objects. Rare in modern interfaces, but still useful when the metaphor itself carries meaning, such as a leather-bound notebook for notes.
The practical rule: pick one style and stay in it. A screen that mixes flat, skeuomorphic, and outline icons looks assembled rather than designed.
Criteria for choosing an icon set
Consistency
Check stroke width, corner radius, grid size, and visual weight across the whole set. A set where one icon is noticeably heavier than its neighbors will look broken in a toolbar.
Scalability
Ask for the formats and sizes you actually need — commonly SVG for UI, plus PNG exports at 1x, 2x, and 3x for raster use. Vector source matters because you will need to resize, recolor, and adapt icons later.
Licensing
This is where most teams get caught. Read the license for:
- Commercial use in a product you sell
- Modification (recoloring, reshaping)
- Redistribution inside an app bundle or design system
- Attribution requirements
A free set is not automatically free for every use. Check the specific terms rather than assuming.
Platform guidelines
Apple's Human Interface Guidelines and Google's Material Design both publish icon guidance, including recommended sizes and which metaphors are already taken. Following them reduces the chance that users misread your icons. If you are building for one platform, its conventions should usually win over a generic set.
How icons work in UI/UX
Icons speed up recognition and shrink the space a control needs. They work best when paired with a text label, especially for anything unfamiliar — an icon alone is a guess, an icon plus a word is an instruction.
Use icons for:
- Navigation (home, search, profile)
- Common actions (edit, share, delete)
- Status and feedback (success, warning, offline)
Be careful with metaphor. A floppy disk for "save" still works for many users, but a younger audience may not recognize it. When a metaphor is ambiguous, label it.
Steps to source or commission custom icons
- Audit what you need. List every action, object, and state that requires an icon. Group them so related icons share a visual family.
- Define the spec. Decide grid size, stroke width, corner radius, color rules, and export formats before anyone draws anything.
- Choose a path. Use an existing set if your needs are common; commission custom icons if your product has unique concepts, a strong brand system, or a need for a distinctive look.
- Test at real size. View the icons at the smallest size they will appear, on the actual background colors. Problems that are invisible at 200px show up immediately at 20px.
- Document and hand off. Name files predictably, keep the vector source, and record the license. Future you will need it.
For custom work, a studio that has spent decades on icon and interface design — like The Iconfactory, which has crafted icons, apps, and user experiences for clients for over 25 years — is the kind of partner to evaluate against your spec, not instead of it.
Quick decision guide
- Shipping fast, common actions? Use a well-licensed existing set and follow platform guidelines.
- Distinctive brand, unusual concepts? Commission custom icons with a written spec.
- Mixed needs? Start from a base set, then commission only the icons it lacks — but match the style precisely, or the seams will show.