Picking a style

—
Line icons

The most used icon style—these icons are built with open strokes, showing a minimalist and lightweight appearance. Their consistent stroke width creates visual harmony, and they pair very well with most used typefaces (Inter, Helvetica..) and minimalist interfaces.

Core icons by Streamline

Pros

• Clean, elegant, and easy to integrate with minimalist designs.
• Lightweight style, with a lot of negative space inside, that makes design using it more airy. 
• Pair well with lightweight typography.

Cons

• Less legible at smaller sizes.
• Less legible on dark or complex backgrounds.
• May lack visual impact in bold designs.

Best for

• User interfaces (UI) for modern web and mobile apps.
• Wireframes, mockups, and prototypes.
• Minimalist dashboards and SaaS platforms.
• Brands emphasizing simplicity.

—
Solid icons

Solid icons shout loud without words—bold, simple shapes that command attention, ensuring effortless readability on any screen or signage, and thriving where clarity and instant recognition are essential.

Core and Flex Solid by Streamline

Pros

• Highly legible even at small sizes.
• Strong contrast on busy or dark backgrounds.
• Excellent for alerting or emphasizing key UI actions.
• Ideal for color customization.

Cons

• Can feel heavy or overpowering in minimal designs.
• Less flexible in adapting to light themes without customization.

Best for

• Call-to-action buttons and key interaction points.
• Navigation menus in mobile apps.
• Icons for signage or visual instructions.
• Digital products requiring bold, simple communication.

—
Duotone Icons

A perfect style for branding—these icons combine two contrasting tones to add depth and visual interest. The shapes are defined by a dark stroke, while the second tone fills the shape with color, resulting on legibility and a vibrant visual appeal.

Core and Flex Duotone by Streamline

Pros

• Adding dimension and colors to minimalist designs.
• Works well with branding by using the main brand color as an accent.
• Creates a subtle sense of depth.

Cons

• Less legibility than Line or Solid style.
• May not suit ultra-minimal interfaces.
• Needs a bigger scale to maintain legibility.

Best for

• Branding visuals with distinct color palettes.
• Marketing materials and creative campaigns.
• Websites and apps that need banding colors.

—
Hybrid icons

The ideal blend of simplicity and impact—these icons combine bold solid shapes with light, minimalist lines. The balanced composition, with consistent stroke weights, creates a design that is both minimal and strong, without overwhelming the interface.

Core Remix, Plump and Flex Remix by Streamline

Pros

• Highly legible: Solid elements anchor the design, while lines provide clarity and subtlety.
• Modern and trendy.
• Flexible: Works in both light and dark themes.
• Great for customization: Easily adaptable with brand colors.
• The combination of lines and solid black areas creates a hand-drawn, inked effect.

Cons

• Requires careful design to avoid imbalance.
• Thin line details can lose clarity at smaller sizes.

Best for

• Modern branding where strength and subtlety coexist.
• Minimalist design and interface, where legibility is needed.
• Works well as illustrations, on a bigger size (from 64px).

—
Flat Icons

Bold and contrasted—the flat icon style eliminates depth, focusing on simplicity, clarity, and clean shapes. It relies on bold, contrasting colors for instant recognition and strong visual impact. 

Core Flat icons, Flex Flat icons by Streamline

Pros

• Bold and Solid Appearance: Delivers a strong visual impact.
• Perfect for Branding: Works well with two-color schemes.
• Great for graphic design, used for adding splashes of colors.
• Highly Legible: Strong shapes and minimal details ensure clarity, especially when using bold, contrasting colors.
• Timeless and Modern: bold solid shapes create a contemporary, striking look.

Cons

• Can lack depth and uniqueness.
• Oversimplification may lead to less distinctive designs.
• May lose legibility when using light/pastel colors or overly contrasting combinations.
• A bold style that can feel overwhelming if not balanced properly.

Best for

• Modern mobile and web interfaces.
• Branding usage

—
Pixel Icons

Old-school retro charm—these icons are built on a strict pixel grid, embracing the limitations of early computer displays. Their blocky, low-resolution aesthetic evokes a nostalgic, vintage feel, reminiscent of classic video games and early digital interfaces.

Free Pixel icons by Streamline

Pros

• Crisp and precise at small sizes.
• Appeals to retro and gaming aesthetics.
• Can scale for illustrative needs if built as vector svg.
• Pair well with pixel typefaces.

Cons

• Limited scalability if made as pixel file like png—can become blurry when enlarged.
• Less versatile in modern, sleek designs. It got a strong vintage connotation.

Best for

• Retro-themed digital products or gaming apps.
• Small UI elements like toolbars and badges.
• Low-resolution digital interfaces.
• Brands leaning into nostalgic, vintage design styles.