Proofreading is an iterative process of comparing galley proofs against the original manuscripts or graphic artworks to identify transcription errors in the typesetting process. In the past, proofreaders would place corrections or proofreading marks along the margins. In modern publishing, material is generally provided in electronic form, traditional typesetting is no longer used and thus (in general) this kind of transcription no longer occurs. Consequently the part played by pure proofreaders in the process has almost vanished: the role has been absorbed into copy editing to such an extent that their names have become interchangeable. Modern copy-editors may check layout alongside their traditional checks on grammar, punctuation and readability.
Professional
Traditional method
A "galley proof" (familiarly, "a proof") is a typeset version of copy or a manuscript document. It may contain typographical errors ("printer's errors"), as a result of human error during typesetting. Traditionally, a proofreader looks at an portion of text on the copy, compares it to the corresponding typeset portion, and then marks any errors (sometimes called "line edits") using standard proofreaders' marks. Unlike copy editing, the defining procedure of a proofreading service is to work directly with two sets of information at the same time. Proofs are then returned to the typesetter for correction. Correction-cycle proofs will typically have one descriptive term, such as "bounce", "bump", or "revise" unique to the department or organization and used for clarity to the strict exclusion of any other. It is a common practice for all such corrections, no matter how slight, to be sent again to a proofreader to be checked and initialled, thus establishing the principle of higher responsibility for proofreaders as compared to their typesetters or artists.
Alternative methods
"Copy holding" or "copy reading" employs two readers per proof. The first reads the text aloud literally as it appears, usually at a comparatively fast but uniform rate. The second reader follows along and marks any pertinent differences between what is read and what was typeset. This method is appropriate for large quantities of boilerplate text where it is assumed that there will be comparatively few mistakes.
Experienced copy holders employ various codes and verbal shortcuts that accompany their reading. The spoken word "digits", for example, means that the numbers about to be read are not words spelled out; and "in a hole" can mean that the upcoming segment of text is within parentheses. "Bang" means an exclamation point. A "thump" or "screamer" made with a finger on the table represents the initial cap, comma, period, or similar obvious attribute being read simultaneously. Thus the line of text (He said the address was 1234 Central Blvd., and to hurry!) would be read aloud as "in a hole [thump] he said the address was digits 1 2 3 4 [thump] central [thump] buluhvuhd [thump] comma and to hurry bang". Mutual understanding is the only guiding principle, so codes evolve as opportunity permits. In the above example, two thumps after buluhvuhd might be acceptable to proofreaders familiar with the text.
"Double reading" is when a single proofreader checks a proof in the traditional manner and then another reader repeats the process. Both initial the proof. Note that with both copy holding and double reading, responsibility for a given proof is necessarily shared by the two proofreaders. Recently, artificial intelligence (AI), such as ChatGPT by OpenAI, has been used in this process; however, there is deep concern about the effectiveness of using artificial intelligence for a human task like editing.
"Scanning" is used to check a proof without reading it word for word, has become common with computerization of typesetting and the popularization of word processing. Many publishers have their own proprietary typesetting systems, while their customers use commercial programs such as Word. Before the data in a Word file can be published, it must be converted into a format used by the publisher. The end product is usually called a conversion. If a customer has already proofread the contents of a file before submitting it to a publisher, there will be no reason for another proofreader to re-read it from the copy (although this additional service may be requested and paid for). Instead, the publisher is held responsible only for formatting errors, such as typeface, page width, and alignment of columns in tables; and production errors such as text inadvertently deleted. To simplify matters further, a given conversion will usually be assigned a specific template.