FC0-U71 Tech Concepts and Terminology Practice Question
A user notices that a file saved as a JPEG is smaller than the original BMP file. Which type of compression does JPEG typically use?
⚠ Common exam trap
FC0-U71 often tests the misconception that JPEG uses lossless compression because it reduces file size without obvious quality loss, but the key is that it is lossy and discards data.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Lossy compression
JPEG typically uses lossy compression, which reduces file size by permanently discarding some image data, especially high-frequency color details that the human eye is less sensitive to. This is why a JPEG is much smaller than the original BMP, which is uncompressed. The trade-off is a slight loss of quality, but the size reduction is significant.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Lossy compression
Why this is correct
JPEG discards high-frequency colour and luminance detail the human eye barely registers, so file size drops sharply against the uncompressed BMP. That irreversible data removal is lossy compression, the axis distinguishing it from lossless formats such as PNG.
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Run-length encoding
Why it's wrong here
JPEG uses lossy DCT-based compression, discarding high-frequency detail; run-length encoding is a lossless scheme that collapses consecutive identical values, suited to paletted images such as TIFF or PCX, not photographic JPEGs. It is tempting because RLE genuinely shrinks files, but it cannot deliver JPEG's typical photographic reduction.
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Uncompressed
Why it's wrong here
JPEG is inherently compressed, so labelling it uncompressed contradicts the stem's observed size reduction. Uncompressed formats such as BMP store raw pixel data, which is precisely why the original BMP was larger. It is tempting as a baseline, but JPEG's DCT quantisation removes data, so the file cannot be uncompressed.
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Lossless compression
Why it's wrong here
JPEG uses lossy compression, discarding colour and frequency detail to shrink files substantially. Lossless compression preserves every pixel exactly and is correct for formats such as PNG or GIF where no image data may be discarded.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official CompTIA exam blueprint
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