What tone of voice consistency actually means
Tone of voice is the set of choices a piece of copy keeps making the same way: how formal the words are, whether it says "you" or "we", how long its sentences run, whether it uses contractions. None of these choices matters much on its own. What a reader notices, usually without being able to name it, is when the choices stop agreeing with each other from one paragraph to the next.
A page reads as consistent when a stranger could not tell that two different people, or a person and an AI tool, wrote different sections of it. That is the standard worth checking against.
Where the drift usually happens
Inconsistency rarely shows up as one glaring mistake. It shows up as a homepage written by one person, a product page added six months later by someone else, and an email template drafted in a hurry by whoever was free that week. Each piece reads fine alone. Put side by side, one calls the reader "you" and the next says "our customers". One is full of short, direct sentences and the next runs long and formal, as if it were nervous about sounding too casual.
AI-drafted copy adds its own version of the problem. Left without a brief, a writing tool defaults to a register of its own, usually warmer and vaguer than most brands intend, and it will hold that register confidently across a whole page even where the surrounding copy does not match it. The fix is not to distrust the draft outright. It is to check it against the same markers you would check any other draft against.
The markers worth checking, line by line
- Person: does the copy consistently say "you", "we", or a mix, and is the mix deliberate
- Contractions: does one section write "it's" and the next write "it is" with no reason for the change
- Sentence length: does one paragraph run in short, clipped lines and another stretch into long, formal ones
- Vocabulary weight: does the copy reach for plain words in one place and dressed-up ones ("leverage", "optimise", "elevate") in another
- Address to the reader: does it instruct ("you should") in one section and describe ("customers often") in the next
None of these is a rule with a single right answer. A page can legitimately switch from short instructional sentences in a how-to section to longer explanatory ones in a background section. What is worth catching is the switch nobody chose, the one that happened because two different people, or a person and a tool, wrote two different parts of the same page.
Checking your own copy for it
Reading the whole page aloud, start to finish, catches most of what matters. A sentence that sounds like a different person wrote it usually announces itself the moment you say it out loud, even if it passes a silent read.
Beyond that, it helps to write down your own choices before you check anything. A short reference, three or four lines, stating whether you use "you" or "we", whether contractions are in or out, and roughly how long your sentences run, gives you something concrete to check new copy against. The guide to defining and documenting your tone of voice sets out how to build that reference properly, and the pre-publish checklists give you a line-by-line pass to run before anything goes live.
What a check like this cannot settle for you
Consistency is a pattern you can check for. Whether the pattern is the right one for your business is a judgement call that stays with you. A page can be perfectly consistent and still be the wrong voice for the reader in front of it, formal where it should be plain, or breezy where the subject calls for care. Checking for consistency tells you whether your choices agree with each other. It does not tell you whether they were the right choices to begin with.