The difference between an automatic document feeder and a flatbed scanner
Quick definition
An automatic document feeder (ADF) pulls a stack of pages through the scanner one at a time. A flatbed scanner has a glass surface where individual pages are placed manually. Most office MFPs include both — the ADF for multi-page documents and the flatbed for bound originals, fragile pages, or single sheets.
What each is good for
| Component | Best for |
|---|---|
| Automatic document feeder (ADF) | Multi-page loose documents, contracts, reports, batch scanning |
| Flatbed scanner | Bound originals, photos, fragile pages, single sheets, ID cards |
| Dual-pass ADF | Duplex scanning where both sides need separate scanner passes |
| Single-pass duplex ADF | Duplex scanning at full speed with both sides captured simultaneously |
ADF capacity considerations
Office MFP ADFs typically hold 50-100 sheets at a time. Production-class devices hold 200-500 sheets. The ADF capacity matters for multi-page batches — feeding the device with the full batch is faster than splitting into smaller loads. Single-pass duplex ADFs scan both sides of each page during one pass through the feeder, doubling effective throughput compared to dual-pass devices that must run each page through twice.
When to use the flatbed instead
The ADF cannot handle several document types. Bound books and magazines must use the flatbed because the spine prevents single-page feeding. Fragile or aged documents that the ADF might damage should scan on the flatbed. Original photographs benefit from flatbed scanning at higher resolution. ID cards and small documents below the ADF's minimum size must use the flatbed.