An ADF document scanner feeds a stack of pages one sheet at a time past the scan head, so you digitize dozens of pages in one batch instead of lifting each onto the flatbed.
Load the stack, square the edges, pick the feeder as your source, hit scan, collect the file. The feeder handles the pages; your job is preparation.
ADF stands for Automatic Document Feeder — a tray plus rollers on top of the scanner that moves sheets past the scan head untouched. Duplex models capture both sides in one pass; simplex models scan one side, then you flip the stack and run it again.
Lexmark describes the ADF as the feeder for multiple-page documents and notes duplex pages can be scanned through it. That distinction matters, because simplex and duplex feeders look nearly identical.
How Does the Paper Actually Move Through an ADF?
Rollers and a separation mechanism pull one sheet at a time from the bottom of the stack, walk it past the scan head, and deposit it in the output tray. The separation pad keeps two stuck pages from entering together — and wears out first.
Duplex models flip the sheet internally and read the reverse side on the same trip. Simplex models read the front, eject the page, and leave the back for a second pass you run by hand.
Specs vary widely, so treat these as examples. Both are correct — for their machines.
| ADF Spec | What It Means in Practice | Typical Example |
|---|---|---|
| Capacity | Pages you can load before reloading | 50 to 100 sheets |
| Scan mode | Whether the back side needs a second pass | Simplex or duplex |
| Minimum document size | Smallest sheet the rollers grip reliably | 5.8 x 8.3 in. |
| Maximum document size | Longest sheet that clears the path | 8.5 x 14 in. |
| Media weight range | How thin or thick a sheet can be | 14 to 32 lb |
| Daily duty cycle | Volume the feeder is built to handle | Model-dependent |
| Output tray | Where finished pages collect | Rear or front exit |
Which Way Do You Load the Pages?
It depends on the model, and guessing wrong produces blank or upside-down scans. Lexmark’s guidance is faceup, short edge first. A Xerox scanner manual instructs the opposite: face down, tops leading into the feeder. Orientation lives in your model’s manual, not a general rule. If the first scan comes out reversed or blank, flip the stack and rerun — ten seconds.
Alignment matters too: a Xerox manual recommends bending and flattening the stack and squaring edges before loading, the standard defense against skew and multiple-sheet feeds. Fan the pages, tap them flat, load. Zebra’s documentation covers feeder setup as a distinct configured step, reflecting the same principle: the feeder is configured, not just filled.
What Should Never Go in an ADF?
Anything fragile, unusually small, or unusually thin belongs on the flatbed. Lexmark’s list is specific: postcards, photos, small items, transparencies, photo paper, and thin media like magazine clippings should not be loaded into the ADF.
The reasons are mechanical. Coated photo surfaces slip against rollers. Transparencies flex and jam. Small items get pulled in crooked or not at all. Magazine clippings are too light for the separation mechanism to register as a single sheet.
Staples, paper clips, and folded corners are the other culprits. A staple can scar the rollers and scan glass, and repairs cost far more than the two seconds it takes to pull it out.
When comparing feeders, check duplex support and capacity before price. Our breakdown of tested ADF document scanner picks for home offices covers which models handle two-sided batches without a second pass.
FAQs
Can an ADF scan both sides of a page automatically?
Only if the model is duplex-capable. Duplex feeders flip each sheet internally and capture both sides in a single pass. Simplex feeders read one side only, so you flip the stack and run it again. Check your manual before assuming two-sided scanning is included.
How many pages can I load at once?
It varies. Load fewer than the maximum for thick or curled paper, since overloading is a common cause of jams.
Why do my scans come out upside down?
The stack is loaded in the wrong orientation for your model. Some feeders want pages faceup and short edge first; others want them face down with tops leading. Flip the stack, rescan, and record the correct direction.
What causes double-feeds in an ADF?
Misaligned, curled, or staticky pages. Bend and flatten the stack and square the edges before loading. If double-feeds persist on a clean, flat stack, the separation pad is likely worn and needs replacing.
References & Sources
- Lexmark. “Understanding the ADF and Scanner Glass.” Source for ADF definition, loading orientation, capacity and media specs, and the list of items that should not go in the feeder.
- Xerox. “Xerox Scanner User Guide.” Source for face-down loading instructions, the 100-page capacity figure, and the stack-flattening anti-jam step.
- Zebra. “123Scan ADF Documentation.” Source for feeder setup as a distinct configured step in the scanning workflow.