Reading order is the sequence in which a system extracts and interprets the text on a CV, and it matters for an applicant tracking system because a layout that looks perfectly ordered to a human eye can still get read in a jumbled, out-of-sequence way by software that does not understand columns, floating boxes or visual grouping the way a person does. A CV can be well organised visually and still have a confusing reading order underneath it, and the two are worth checking separately rather than assuming one guarantees the other.
What reading order actually means
A human reader looking at a page uses spatial and visual cues, proximity, alignment, a heading's size, to work out which piece of text belongs with which, and does this instantly without thinking about it. Most parsing software works differently: many systems extract text roughly left to right and top to bottom through the underlying document structure, without truly understanding that a box on the right side of the page is a separate, self-contained section rather than a continuation of whatever sits on the left at the same height. When a layout matches that simple top-to-bottom, left-to-right assumption, the system's reading order and a human's visual reading order land on the same sequence. When it does not, the two diverge, and the system's version of the CV can end up considerably harder to make sense of than the one a person sees on screen.
Why a single-column layout keeps reading order predictable
A single-column CV, where every section runs the full width of the page in one stacked sequence, keeps the visual reading order and the extracted reading order aligned almost by construction, since there is only ever one path through the content and no side-by-side content competing for the same vertical space. The Classic template is built this way, with every section stacked in the same order a human would naturally read it, which is also the order most parsing software will extract it in. That alignment is the real advantage a single column offers for reading order specifically, separate from how plain or how visually appealing the layout looks.
Where a multi-column layout can jumble reading order
A two-column layout places two different streams of content, commonly experience in the main column and skills or credentials in a side column, at the same vertical position on the page. A human eye handles this easily, reading down one column and then the other, but a system extracting text by vertical position can interleave a line from the side column into the middle of a sentence from the main column, since both sit at a similar height on the page even though they belong to entirely separate sections. This does not mean every two-column CV reads badly to every system; some modern parsers handle columns correctly. It does mean the risk is structural to the layout itself, not something that depends on how carefully the content within it was written.
Illustrative example: a layout that reads top-to-bottom against one that jumps between columns
Illustrative comparison of the same content in two layouts. In a single-column layout: the summary appears first, followed by experience in full width, followed by education, followed by skills, each section beginning only after the previous one ends, so a system extracting the text in order encounters exactly the sequence a human would also read. In a two-column layout: experience runs down the left column while a skills list and a short certifications block run down the right column at the same height, so a system reading by vertical position can extract a skill or a certification line in the middle of an unrelated sentence describing a job, producing a garbled record even though the visual page looked entirely clear to a human looking at it on screen.
What layout choices affect reading order beyond columns
Columns are the largest factor, but not the only one. Text placed inside a table can be skipped entirely by some parsers rather than read in any order at all, since a table is structured as a grid rather than a flowing sequence of text. A header or footer holding contact details can also fall outside the reading order some systems extract, since headers and footers are sometimes treated as page furniture rather than document content. None of this means any specific layout will necessarily fail, or that a single column will necessarily work cleanly with every system in use; it means the safer layout choices are the ones that keep content in one flowing, top-to-bottom sequence rather than relying on a reader, human or otherwise, to infer the right order from visual position alone.
What this does not guarantee
None of the layout choices above make a CV immune to a parsing problem, since different systems handle the same layout differently, and there is no reliable way to test a document against every system in use before it is submitted somewhere. What a predictable, top-to-bottom reading order does is remove one specific, well-understood category of risk, the risk of two unrelated sections getting interleaved into a single garbled record, without needing to know in advance which system a given employer happens to use. Writing an ATS-friendly resume covers the wider set of layout and formatting choices that affect parsing beyond reading order alone, including file format and section headings.
Checking your own layout
If your current CV uses a multi-column layout, choosing between a one-column and two-column CV layout covers how to weigh the tradeoff between the two, reading order being one factor among several worth considering rather than the only one.
Build yours
Start from the builder, choose a single-column template if reading order is a real concern for the roles you are applying to, and check the resulting document reads in the same order a person would expect before submitting it anywhere.