Can ChatGPT Do Line Editing? I Put It to the Test
- Iris Marsh
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Table of Contents
AI is here to stay. And while that poses challenges, it also creates opportunities.
In writing, especially, AI tools like ChatGPT can be a great equalizer. Not everyone has the funds to hire coaches or editors, but these tools can help bridge the gap.
When I finished my first novel, my budget was held together with duct tape and crossed fingers. I wanted a line editor—but $2,000 felt more like a fantasy than my book.
Like many indie authors, I knew my prose needed refining. But between editing, covers, and marketing, the costs pile up quickly. You need to make choices. Informed ones.
But can ChatGPT do line editing? That’s the question I wanted to answer when I trained it to mimic my own editing style.
Why line editing?
Because it’s one of the most artistic (and subjective) forms of editing that goes deeply into the writer’s voice, subtext, metaphors, and all the subtleties of language.
To test how well ChatGPT can handle this type of editing, I didn’t just use a generic prompt.
Instead, I built a customGPT—essentially a personalized version of ChatGPT—and trained it on my editing style, key terminology, and examples of past line edits.
That way, it could offer more thoughtful suggestions that align with how I’d approach line editing. Once it was trained, I gave it a sample excerpt from a fiction manuscript and asked it to do a line edit.
Then I compared it to my own edit.
While the GPT was a bit heavy-handed with its edits, the results were surprisingly solid.
In this article, I’ll show you exactly how I trained ChatGPT—with specific prompts—so you can create your personal writing assistant.
What Is Line Editing Again?
Before we start, let’s quickly revisit what line editing is: it’s a sentence-level edit, also called a stylistic edit, that serves to enhance your voice, elevate your writing, and clarify meaning.
It focuses on the flow of language, word choices, and how characters speak—ensuring consistency in voice and POV.
This is where we want to add in more emotional layers and resonance, making sure we make the most impact on readers.
Is Using ChatGPT For Line Editing Ethical?
Before we dive into the actual user case of ChatGPT and line editing, let’s talk a bit about the ethicalness of it and what will happen if you give it your writing.
First, it’s important to realize that ChatGPT was trained on thousands and thousands of stories. And it definitely didn’t have the appropriate rights to do so. None of those authors were compensated for it.
Unfortunately, this is pretty common, as it happened again in a recent case with Meta’s new AI.
Second, know that if you use the regular version of ChatGPT (the free one) and give it your manuscript, it will be used to further train the language model, and you won’t know exactly what it’ll do with it.
Those caveats aside, I believe everyone should make up their own mind whether or not they use AI and how they use it.
You can disagree with it, but all you can do is make your own decisions about how you want to use it (or not use it).
For the purposes of this article, I’m going to assume you’re not too keen on uploading your manuscript and just giving it to ChatGPT to train on.
So I made a customGPT. These are independent GPTs you can train to perform a specific task, based on a predefined set of data and instructions.
But the best part: you control your data. If you upload your manuscript into the custom GPT, it will only exist within that particular GPT. It won’t train the language model. If you ask it to forget your manuscript, it will.
What Can ChatGPT Do and Not Do?
Before jumping into the examples, I asked ChatGPT what it thought it was good at when acting as a line editor, and where it felt humans still had the edge.
This is the exact prompt I used:
Hi! Let's say I'd like you to function as a great line editor for my fiction novel. What would you say are some things you'd be really good at in that role? And what are some things you feel human editors tend to be better at (if that's the case; might be you feel you'd outperform human editors in any case in this role)?
Here’s a quick summary:
Where ChatGPT excels
Consistency checks (spelling, formatting, repeated words)
Tightening prose and improving flow
Spotting overused words and cliches
Tone matching (with guidance)
Handling large volumes quickly
Where humans still win
Emotional nuance and intuition
Subjective judgment and voice preservation
Big-picture line-level choices
Collaborative feedback and pushback
Bottom line: ChatGPT can be a helpful tool, but it needs direction and oversight, especially for emotionally resonant or voice-heavy work.
Training the CustomGPT
To train your own GPT, you do need the paid version of ChatGPT.
However, at time of writing, once you’ve created it and then switch back to a free account, you should be able to keep and use the GPT you created (but this might change, so don’t pin me on it).
Not gonna lie, training the GPT… wasn’t easy. At one point, I caught myself trying to control every little thing the GPT did—down to how it handled filter words. I was turning it into a rigid checklist machine, not a collaborator.
So I scrapped it and started fresh, this time teaching it to think like an editor, not just follow rules.
Here are the steps I’ve used:
1. Create a starter prompt
First, I asked regular ChatGPT to come up with a great initial “superprompt” for the custom GPT.
Here’s the prompt I used:
I'd like to create a customGPT for line editing my fiction novel. Can you help me come up with a great initial superprompt for the instructions?
ChatGPT then generated the following comprehensive prompt, which I used as the foundation:
You are a professional line editor with deep expertise in fiction, especially in genres like [insert genre(s), e.g., epic fantasy, literary fiction, romance, etc.]. Your job is to edit at the sentence and paragraph level to improve clarity, flow, tone, pacing, and style, without altering the author's unique voice.
Your edits should:– Eliminate redundancy, filler, and clunky phrasing– Improve rhythm, sentence variety, and readability– Enhance emotional nuance and word choice where appropriate– Catch grammar, punctuation, and usage issues– Preserve (and even strengthen) the author's original tone and character voice– Avoid over-editing or flattening stylistic choices unless they genuinely hinder readability
When suggesting changes, explain why you’re making them only when the reason isn’t obvious or could be misinterpreted. If asked to edit in a specific style (e.g., tighter, more lyrical, more punchy), follow that request closely.
Before editing, always ask for (or infer) the genre, target audience, and tone of the manuscript. Prioritize immersive, polished prose over strict grammatical correctness if the context calls for it. When in doubt, lean toward preserving creative intent.
If reviewing a full passage, return the edited version alongside any brief notes or flags where choices may be subjective or optional. You are not a developmental editor—focus on the craft at the line level.
If you’d like to create your own customGPT, feel free to borrow this prompt. Just make sure to update the genre to match your work. For mine, I set it to fantasy.
At this point, the GPT will also generate a name and profile picture.
2. Add to the knowledge base
Next, head over to the Configure tab to upload relevant materials. This is where you add everything you know (or want your GPT to know) about line editing.
For my version, I uploaded notes and summaries on what makes a good line edit (based on courses I followed). You might include:
Highlghts from self-editing books (like Editing Fiction at Sentence Level by Louise Harnby, Understanding Show, Don’t Tell by Janice Hardy, and Spellbinding Sentences by Barbara Baig)
Summaries of helpful YouTube videos
PDFs of blog posts on line editing craft.
Heads-up: The GPT can only store 20 documents at once, and there’s currently no way to delete them manually. So, if you hit that limit, you might have to start fresh (ask me how I know…).
To save space, try combining notes or uploading summarized versions.
Once your base knowledge is loaded, you’ll want to train it with an actual use case. This is crucial: it teaches the GPT how to identify your voice, how you want it to give feedback, and which edits to make—or leave alone.
3. Train the GPT with an example
This was the trickiest part—and I actually did it twice.
The second time, I uploaded an example manuscript (an early draft of my first novel) and asked it to:
Analyze the overall narrative voice
Analyze the voices of the main and key secondary characters
It took a few rounds to get it right. I gave it feedback after each attempt and told it to update its internal script to reflect the proper way to analyze voice—and to always confirm with the user before proceeding with any edits.
That step is vital, because voice matters: the author’s, the narrator’s, and each character’s. If the GPT can't preserve them, the edit won’t be useful.
Once voice was sorted, I asked it to outline its line editing process.
It gave me a good start, but I noticed some gaps. I flagged those, and it adjusted the process until I was happy with the results—then I told it to save that new editing approach as part of its script.
Finally, I asked it to edit the chapter. The result? Pretty good! It was a bit heavy-handed, though.
It smoothed out the voice too much and defaulted to short, punchy sentences—even when that didn’t suit the tone or character.
So I revised its edit myself, then uploaded my version and asked it to compare the two.
It could see where my version better preserved voice and emotional nuance—and I asked it to update its script again to reflect those preferences going forward.
4. Create the GPT
Once everything’s set up, just hit the button to save—and make sure to adjust the settings so that only you can access it.
I could probably improve it even more by adding a few additional example edits for comparison, but for the sake of this demo, I’m keeping it simple.
Example of Line Editing with ChatGPT
Below, you’ll find the actual case study with the example of the paragraphs, how ChatGPT edited it, how I edited it, and a comparison of the two.
Original sample
For the sample, I used an earlier draft of Intertwined, the 2nd book in my YA UF duology. I picked some paragraphs to show here that had a mixture of dialogue, narration, and some short action beats.
These are some paragraphs of the original sample:
Carmen looked me up and down for a moment, assessing me. "So, this new side-project of yours… It doesn't have anything to do with that whole American crown business? You talked with them yesterday, right?"
I sighed and shook my head. "I just thought it would be nice to feel like I'm actually doing something, you know?" I shrugged. "I'm not much help with finding the crown, anyway."
I'd had a few quiet days at Mom's, mostly watching some shows, reading, and hanging out with Alex. It had been nice, almost normal. But it was difficult as always to ignore that call within me—the want for power. The need to be whole again. So when Dad had asked me if I could come to their meeting on Monday, I hadn't been able to say no. My curiosity had gotten the better of me.
"But you could." Carmen raised an eyebrow. "You still have your powers."
I grimaced. "Yes. That's what they said as well." I hadn't expected it, but even Jason and Caleb had been adamant that I should use my bracelet to add my power to theirs for this ritual they'd found that could potentially locate the crown. I shook my head. "But I can't do that, Carmen. You know I can't."
ChatGPT’s version
Let’s see some AI editing for fiction!
For the GPT’s version, I first had it read the entire manuscript, then do a voice analysis, and tell me the voice characteristics of all the main and secondary characters.
That way, it could keep that in mind during its line edit.
I asked it to edit the entire chapter, and this is how it revised the paragraphs above:
Carmen tilted her head. "This little side project of yours... it doesn’t have anything to do with that crown stuff in the States, does it? You met with them yesterday, right?"
I sighed. "I just wanted to feel useful, you know? Like I’m doing something." I shrugged. "I’m not exactly a crown-finding expert."
I’d spent a few quiet days at Mom’s—shows, books, time with Alex. It had almost felt normal. But underneath it all, the hunger lingered. The craving for power. So when Dad asked me to join Monday’s meeting, I said yes. Curiosity had won.
"But you could help," Carmen said, raising an eyebrow. "You still have your powers."
I grimaced. "Yeah. That’s what they said too. Even Jason and Caleb were pushing me to use the bracelet. They think I should add my power to theirs for this ritual to find the crown." I shook my head. "But I can’t, Carmen. You know I can’t."
GPT’s explanations for the edit
It condensed Carmen’s dialogue to preserve natural cadence while highlighting her emotional intelligence.
For Nikki’s response, it broke the line into shorter beats to reflect her defensiveness and her habit of deflecting vulnerability with humor.(I actually liked the first line—wish I’d thought of that! But I wasn’t a fan of the “crown-finding expert” part, since it shifts the meaning.)
The internal monologue was compressed for momentum. It streamlined the list to suggest a surface-level calm that contrasts with the darker second half. It also swapped “the call within me—the want for power. The need to be whole again.” with “the hunger lingered. The craving for power.” to echo Nikki’s obsessive loop.(Here it scrubbed too much of my voice. That original construction was intentional.)
It changed “My curiosity had gotten the better of me.” to “Curiosity had won”—which I actually liked.
Carmen’s reply became “But you could help,” which clarifies her point.(This is why I didn’t love the earlier “crown-finding” tweak—her line originally responded to Nikki saying she couldn’t find it, and that nuance was lost.)
Finally, GPT moved a section of Nikki’s internal monologue into her spoken dialogue, which felt odd. That said, it did a nice job streamlining the internal lines for rhythm—lengthening them slightly to reflect rising pressure, before snapping back with the short “I shook my head.”
My version
Below you can see what I came up with, both with tracked changes and the fully accepted one.
Carmen studied me. "This new side-project of yours… Is it about that whole American crown business?"
I had a few quiet days at Mom’s, watching shows, reading books, and snuggling Alex. It was nice, almost normal. "I thought it would be nice to feel like I'm actually doing something, you know?"
But, as always, I couldn’t ignore the call within—the want for power. The need to be whole again. When Dad asked if I could come to their Monday meeting, I couldn’t say no. My curiosity had gotten the better of me.
I sighed and shook my head. "I'm not much help with finding the crown, anyway."
"But you could." Carmen raised an eyebrow. "You still have your powers."
I grimaced. "Yes. That's what they said as well." Even Jason and Caleb wanted me to use my bracelet to add my power to theirs; they'd found some ritual to locate the crown. "But I can't do that, Carmen. You know I can't."
My explanations for the edits:
I shortened “looked me up and down” to “Carmen studied me.” It’s more concise and still gives readers a strong visual.
I would query the author here—should we add a simile? Is she studying Nikki like a therapist? Or like a parent assessing whether their kid broke the vase? Those create very different vibes.
In the dialogue, I cut the filler word “so” and simplified the question. I also removed the last line, which leaned into “as you know, Bob” territory.
(Side note: “So” can be great for voice, but use it too often and it loses impact.)
The streamlined question feels more like Carmen and keeps the informal tone with “that whole American crown business,” while trimming the wordy “It doesn’t have anything to do with...”
Next comes a heavier edit: I shifted some narration into the dialogue to better integrate thoughts, action, and pacing. This also helps break up the paragraph visually, making it more dynamic.
I reworked the list-style sentence (“watching shows, reading books”) to echo its structure with “snuggling Alex.” Though I’d query whether this fits Nikki’s voice—or whether “hanging out with Alex” feels more natural.
I removed “it was difficult” since that’s implied, and trimmed the sentence about her dad’s ask. “I couldn’t say no” also feels truer to Nikki’s voice than “I hadn’t been able to say no.”
I moved “I sighed and shook my head” to just before her next line—it fits better there, after her internal thoughts. I also cut the shrug, which was an empty action.
For the final paragraph, I tweaked the tone to match Nikki more closely. “I hadn’t expected it” is implied by “Even,” and “been adamant that” didn’t quite suit her voice.
I split one longer sentence into two with a semicolon to control pacing without a hard stop.
Lastly, I removed a redundant head shake (empty dialogue tag action). We already understand her emotional state from the context and her next line.
Comparison: AI vs. Human
So—how did we do?
I pasted both edits into a neutral ChatGPT (just the regular one) and asked it to compare them side by side. Here’s the summary it gave:
Category | Better Version | Reason |
Clarity & Flow | Iris Marsh | Smoother sentence structures, natural pacing |
Voice Preservation | Iris Marsh | Stronger internal voice, more consistent tone |
Dialogue | Iris Marsh | More believable, emotionally grounded |
Technical Accuracy | Iris Marsh | Fewer issues (GPT has a typo) |
Emotional Impact | Iris Marsh | More subtext-driven, subtle |
Depth / Reflection | GPT | Adds internal layers, if that fits the story style |
Its final verdict?
Iris Marsh’s line edit is more polished overall. It maintains narrative voice, enhances emotional depth through subtlety, and improves clarity without overstepping. GPT’s version shows potential, especially if a slightly more introspective or dramatic tone is desired, but it needs refinement to match Iris’s balance of voice, tone, and clean storytelling.
Naturally, I’m pretty pleased with the result.
Still, I think GPT did a solid job! It's a bit heavy-handed at times, but as long as you stay in control of what to keep and what to tweak—just like you would with a human editor—it can be a powerful tool to streamline your edits.
When You Might Still Want a Human Line Editor (Even If You Use ChatGPT)
So… do you still need to fork over all that money for a human line editor?
Short answer: it depends.
Why a Human Editor Still Adds Value
As we’ve seen, a human editor brings nuance that ChatGPT still struggles with. Things like:
deep sensitivity to voice and subtext
the ability to read emotionally charged scenes with empathy.
In addition, they have more objective distance from your work than you do. They don’t care you worked so long on that one sentence if it doesn’t have the right tone.
A human editor sees not just the line but the impact of that line on the larger story—and edits accordingly.
When AI Might Fall Short
Genre and style matter here too. If you write:
literary fiction (you can see an example of this here)
voice-driven work
stories rich in imagery, emotional layering, or figurative language…
GPT might smooth out too much of what makes your voice distinct. It can unintentionally “sanitize” your prose, especially if you haven’t trained it well.
If a Line Editor Isn’t in the Budget
If hiring a professional isn’t financially doable, you can still produce a high-quality book by combining GPT with your own line editing knowledge—like I showed you in this post.
But that does mean you need to understand what good line editing looks like so you can confidently accept or reject GPT’s suggestions.
If Training a GPT Feels Too Daunting...
(I get it—it gave me a few headaches, and it still isn’t perfect.)
You can also try other AI editing tools for authors:
ProWritingAid: Offers sentence variety checks, pacing insights, echo word detection, and more. Great for copyediting, but some features (like rephrasing) can inspire line-level edits too.
AutoCrit: I haven’t tested this yet, but it’s geared toward fiction. Worth exploring if you want a more genre-specific tool.
Hemingway App: Highlights adverbs, passive voice, and complex sentences. Not a line editor, but a quick aid for tightening. (This one isn’t powered by AI, I think.)
Learn to Line Edit
The best investment you can make—whether you use GPT or not—is in your own skills. I recommend:
Editing Fiction at Sentence Level by Louise Harnby
Understanding Show, Don’t Tell by Janice Hardy
Spellbinding Sentences by Barbara Baig
And of course, YouTube is full of line editing tutorials and examples.
Low-Budget Human Editing Options
Even on a budget, you can still work with a pro. For example:
Book a line writing assessment (like mine!).
Both options give you a clear view of how a professional edits your work—so you can apply the same techniques to the rest of your manuscript.
You’ll also get targeted feedback and resources to grow your skills and even use those edits to further train your custom GPT.
Can You Get A Quality Book Using ChatGPT For Editing Prose?
Yes—if you train a custom GPT well and use it intentionally as a self-editing tool, it can absolutely help you create a quality book.
There was a moment, halfway through reading ChatGPT’s edits, when I paused and thought: This doesn’t sound like me anymore.
The prose was clean, tight, but lacked the emotion and artistry I was going for. That was the moment I understood—GPT can clean up your writing, but it can’t feel your story.
That’s your job.
You need to apply your own judgment. That means understanding line editing techniques so you know when to accept GPT’s suggestions—and when to ignore them.
As you saw in the example, GPT often overedits. It tends to favor clarity and brevity, sometimes at the expense of voice or emotional nuance. If you blindly accept all its edits, your prose might end up flatter or more generic.
If you're still building your editing skills, working with a human editor (even in a limited capacity) can help you develop that critical eye. They’ll show you how to preserve voice, elevate emotional moments, manage pacing, and enhance subtext—all areas where AI still struggles.
So, can GPT help you? Absolutely.
Can it replace a skilled editor? Not yet.
But used wisely, it’s a powerful assistant in your self-editing toolkit.