# Optical Scan Voting System An **optical scan voting system** reads marks on a paper ballot and tallies them. It is the machine that counts most American votes: the voter marks a paper ballot by hand, or a [[Ballot Marking Device]] prints one, and a scanner turns the marks into numbers. Because the paper outlives the count, every audit, recount and adjudication fight runs through this machine, and so does the [[Election Denialism]] push to get rid of tabulators. ## How the scanner reads a ballot A modern scanner images each ballot and looks for marks inside the voting targets. A 2015 [[National Institute of Standards and Technology]] study (NISTIR 8069) describes two methods: counting dark pixels in a target against a threshold, or edge detection. Vendors set the thresholds and generally do not publish them, and NIST found that "no two sensors are identical." Each ballot yields a share of the tally, a [[Cast Vote Record]] and, in most current systems, a stored image, all gathered by the [[Election Management System]]. ## Where the scanner sits Where the scanner sits is the most consequential design choice in American vote counting: - **Precinct-count optical scan (PCOS)** — the scanner is in the polling place. The voter is still present when the ballot is read, so the system can reject an overvote and hand the ballot back. This is the only architecture in which the federal second-chance guarantee at 52 U.S.C. § 21081(a)(1)(A)(iii) actually operates. - **Central-count optical scan (CCOS)** — ballots are transported to a county facility and scanned in batches. Nobody is standing next to the scanner, so a rejected ballot goes to [[Ballot Adjudication]] rather than back to the voter. All mail ballots are counted this way. ## Marginal marks A marginal mark is "neither clearly countable as a vote nor clearly countable as a non-vote" (the [[Election Assistance Commission]] definition): a check, an X, a partial, heavy or light fill. The scanner's threshold decides which it counts, ignores or sets aside for [[Ballot Adjudication]]. Georgia alone writes the threshold into rule: under Rule 183-1-15-.02, 20% fill or more is a vote, under 10% is not, and the band between goes to a review panel. Elsewhere the number sits in the vendor's configuration. See [[Ballot Marking Validity Crosswalk]]. ## Who uses them [[Verified Voting]]'s data, projected for 2024, put about **69%** of registered voters where most voters hand-mark paper for a scanner, about 25% where every in-person voter uses a BMD (whose printouts are also scanned), and about 5% on paperless machines (one secondary report, PolitiFact 2023). Three firms supply nearly all the equipment. | Vendor | Note | |---|---| | [[Election Systems & Software]] | The largest of the three, based in Omaha | | [[Liberty Vote]] | The former [[Dominion Voting Systems]], bought in October 2025 by [[Scott Leiendecker]], a former Republican election official, and renamed | | [[Hart InterCivic]] | Based in Texas, its home market | ## The hand-count push, 2025–26 On August 18, 2025, [[Donald Trump]] called voting machines "highly inaccurate" and promised an executive order to end mail ballots; legal scholars told NPR the president has no power to set election methods. Georgia's barcode-ballot fight is in [[Ballot Marking Device]]. The measured record cuts against hand counts, which err more and take far longer (Note 2 of [[How a Ballot Is Counted]]). Machine-skeptical security researchers argue instead for hand-marked paper, scanned, then checked by a [[Risk-Limiting Audit]]. ## See Also - [[How a Ballot Is Counted]] · [[Ballot Marking Validity Crosswalk]] · [[Post-Election Audit Crosswalk]] - [[Ballot Marking Device]] · [[Hand-Marked Paper Ballot]] · [[Direct Recording Electronic Voting Machine]] - [[Ballot Adjudication]] · [[Cast Vote Record]] · [[Logic and Accuracy Testing]] · [[Overvote]] - [[Election Systems & Software]] · [[Liberty Vote]] · [[Dominion Voting Systems]] · [[Hart InterCivic]]