SimpleOverlay review
A free, open-source overlay for detailed OpenGL FPS and hardware metrics.
Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026
SimpleOverlay is a GPL-3.0 open-source performance overlay implemented as a native C99 library. It hooks OpenGL swap calls and draws FPS, frame-time, CPU, GPU, VRAM and memory readings over running applications. The project is aimed at Linux, macOS, BSD variants and Illumos users who want an in-game view of rendering and hardware behavior without a hosted service. Desktop and self-hosted deployment suit solo users and small teams that prefer an inspectable codebase.
Its standout capability is metric depth in a compact overlay. The METRICS environment setting controls which readings appear, while NO_GRAPH can disable optional graphs. Additional environment settings adjust position, scale and color, allowing the display to fit different games and desktop layouts. Legacy OpenGL 1.1 support and 32-bit game build and installation support extend its usefulness to older software. A shell wrapper supports ordinary commands and Steam launch parameters, making the overlay applicable both outside and inside Steam workflows.
Platform fit is broad within the OpenGL scope, with the project describing Linux, macOS, *BSD and Illumos support. GPU readings are implemented for AMD, NVIDIA and Apple hardware, while support is provided through documentation. The trade-off is focus: applications using other graphics APIs fall outside the stated target, and configuration is performed through environment variables rather than a dedicated settings interface. Choose SimpleOverlay when open-source delivery, legacy compatibility and detailed OpenGL telemetry matter; consider an alternative if non-OpenGL coverage, broader hardware telemetry or guided configuration is required.
SimpleOverlay pros and cons
- Where it wins
- Displays FPS, frame time, CPU, GPU, VRAM and memory readings
- Supports graphs, metric selection, colors, scale and on-screen position
- Works with legacy OpenGL 1.1, 32-bit builds and Steam launch parameters
- Where it doesn't
- Targets OpenGL applications rather than other graphics APIs
- Configuration is handled through environment variables
- GPU readings cover AMD, NVIDIA and Apple hardware
SimpleOverlay fact sheet, pricing and score →
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