To ensure a GUI layout adapts to different screen sizes, follow these strategies:

1. Use relative units: Instead of fixed pixels, use relative units like percentages, ems, or rems to define sizes and positions.

2. Flexible grids: Employ flexible grid systems, like CSS Grid or Flexbox, that adapt to changing screen sizes.

3. Responsive design: Design multiple layouts for various screen sizes and use media queries to apply them accordingly.

4. Fluid images: Use fluid images that scale with the container, rather than fixed-size images.

5. Adaptive components: Create adaptive components that adjust their size, layout, or behavior based on screen size.

6. Test and iterate: Test the layout on various devices and screen sizes, and iterate on the design to ensure a smooth user experience.

7. Use layout managers: Utilize layout managers that support adaptive layouts, such as Java's GridBagLayout or Android's ConstraintLayout.

8. Prioritize content: Prioritize content and focus on the essential elements, allowing less important elements to adapt or hide as needed.

9. Use breakpoints: Define breakpoints to apply different layouts or styles at specific screen sizes.

10. Keep it simple: Avoid complex layouts and focus on simple, flexible designs that adapt easily to changing screen sizes.

By incorporating these strategies, you can create a GUI layout that effectively adapts to various screen sizes, ensuring a great user experience across devices.