Redline vs Blackline: What's the Difference?
Someone asks you for a blackline. You've always called it a redline. Are they different things? Did you miss something? The short answer: no. A redline and a blackline are the same deliverable. The terms refer to the same document: a comparison showing what changed between two versions of a contract.
The longer answer matters because the terminology creates real confusion in practice. A junior associate who has only heard "redline" may hesitate when a client requests a "blackline." A paralegal switching firms may wonder whether the new firm's "blackline process" is different from the old firm's "redline process." It isn't, but the uncertainty costs time.
This post explains where both terms come from, why the distinction persists, and what actually matters when you're producing or reviewing a comparison document.
Where the terms come from
Both terms have physical origins that predate word processors entirely.
Redline
"Redline" comes from the practice of marking changes on a printed document with a red pen. A lawyer reviewing a draft would strike through deleted language in red, write new language in red, and return the marked-up copy. The red ink stood out against the black printed text, making changes visible at a glance. When word processors introduced Track Changes, the convention carried over: inserted text appeared in red (or another color), deleted text appeared in red with strikethrough. The term "redline" stuck.
Blackline
"Blackline" has a less obvious origin. Before digital tools, one method for comparing documents was to overlay two printed versions on a light table or photocopy them on top of each other. Where the text differed, the overlapping characters produced dark marks or smudges. These black marks at points of difference gave the output its name. Another explanation traces the term to the DeltaView software (later acquired by Workshare, now part of Litera), which early users called a "blackline tool." Regardless of the exact origin, the term became standard in certain practice areas.
Same deliverable, different name
In modern practice, both terms mean the same thing: a document that shows the differences between two versions. When someone asks for a redline, they want to see what changed. When someone asks for a blackline, they want to see what changed. The expected output is identical.
The difference is cultural, not technical. Here is the rough pattern:
| Term | More common in |
|---|---|
| Redline | Litigation, regulatory, government contracts, West Coast firms, smaller firms |
| Blackline | M&A, securities, finance, New York practice, large transactional firms |
| Either | In-house counsel, international practice (varies by jurisdiction) |
These are tendencies, not rules. Plenty of New York M&A lawyers say "redline." Plenty of West Coast litigators say "blackline." The point is that neither term signals a different deliverable. If you receive a request for one and you've always produced the other, you already know how to do it.
When the distinction actually matters
In a small number of situations, practitioners use the two terms to mean slightly different things. This is not standard, but it happens often enough to be aware of.
Redline as Track Changes, blackline as clean comparison
Some lawyers use "redline" to mean a Word document with Track Changes still embedded (so the reviewer can accept or reject changes individually) and "blackline" to mean a clean comparison document that shows changes visually but doesn't contain Track Changes metadata. In this usage, the redline is interactive and the blackline is read-only.
This distinction is useful when it's applied consistently within a team, but it is not an industry standard. Most practitioners use both terms interchangeably for any comparison output.
Blackline in SEC filings
In securities practice, "blackline" often refers specifically to a comparison between successive versions of a filing (such as an amended S-1 registration statement). The SEC may request or expect a blackline showing changes between the original filing and the amendment. In this context, "blackline" is the established term and using "redline" would be unusual.
What this means in practice
If the distinction matters to your counterparty, they will tell you. If they ask for a "blackline" and they want something specific (clean comparison, no metadata), they will specify. If they don't specify, the safe assumption is that they want a standard comparison document showing all changes. Deliver that and you've fulfilled the request regardless of which term they used.
How comparison tools handle it
Every major comparison tool produces the same type of output: a document showing insertions, deletions, and modifications between two versions. The tools don't distinguish between "redline mode" and "blackline mode" because the output format is the same.
| Tool | Output format | What it calls it |
|---|---|---|
| Word Compare | New document with Track Changes markup | "Compared Document" |
| Litera Compare | Document with insertions/deletions marked | "Redline" or "Comparison" |
| Draftable | Side-by-side view with inline changes | "Comparison" |
| Clausul | Full-document view with classified changes | "Comparison" |
The terminology difference in tools mirrors the terminology difference in practice: it is a labeling choice. The comparison itself is functionally identical.
Where tools do differ is in what they detect and how they present it. Word Compare produces a document with Track Changes that you can accept or reject. Dedicated comparison tools typically produce a read-only output that shows changes visually. Some tools classify changes by importance or type. But none of these differences map to the redline/blackline distinction. They are differences in tool capability, not in output category.
What to ask when someone requests one
When a client, partner, or opposing counsel requests a "redline" or "blackline," the right response is not to debate terminology. It is to clarify the deliverable.
Three questions eliminate ambiguity:
- Which two versions should I compare? This is the most important question. A comparison is only as good as the inputs. Make sure you are comparing the right pair of documents. "Please compare the version we sent on Tuesday against the version they returned on Friday" is specific. "Please redline the latest draft" is not.
- Do you want Track Changes embedded, or a clean comparison? This addresses the rare distinction between an interactive document (Track Changes that can be accepted or rejected) and a read-only comparison (changes shown visually but not embedded as Track Changes metadata). Most of the time the answer is "either is fine," but asking prevents a redo.
- Should I flag anything specific? Some requests carry an implicit priority: "blackline this and flag any changes to the indemnification provisions." That tells you the requester cares about a specific section and wants your attention there first. Without asking, you might produce the comparison and move on without the analysis they actually needed.
These three questions take 30 seconds to ask and prevent the most common sources of rework: wrong versions compared, wrong output format, and missing analysis.
The bottom line
Redline and blackline mean the same thing in 95% of legal practice: a document showing what changed between two versions. The terminology difference is historical and cultural, not technical. If you know how to produce one, you know how to produce the other.
The real question is never "redline or blackline?" It is: "Am I comparing the right versions, detecting all the changes, and reviewing the ones that matter?" That's where the choice of comparison tool makes a difference, not the label on the output.
If you want a comparison tool that classifies changes by importance so you can focus on what matters, try Clausul. Call the output whatever your client prefers.
Frequently asked questions
Are redline and blackline the same thing?
They refer to the same concept: a document that shows what changed between two versions. "Redline" comes from the literal practice of marking changes in red ink. "Blackline" comes from the photocopier-era technique where overlaid pages produced black marks at points of difference. In modern legal practice, both terms mean a comparison document showing insertions, deletions, and modifications. The only difference is which word your firm or client prefers.
Why do some firms say blackline instead of redline?
Regional and institutional convention. Firms with roots in New York finance and M&A practice tend to use "blackline." Firms in litigation, West Coast practice, or government contracting tend to use "redline." Neither is more correct. The distinction is cultural, not technical. If your client says blackline, say blackline. If they say redline, say redline.
What is a redline in legal terms?
A redline is a marked-up document that shows every difference between two versions of a contract or legal document. Insertions are typically shown in colored text (often red or blue), deletions appear with strikethrough, and moves or formatting changes may be annotated separately. The purpose is to let a reviewer see exactly what changed without having to read both versions side by side. A redline can be produced by Word Track Changes, by Word Compare, or by a dedicated comparison tool.
What is a blackline comparison?
A blackline comparison is the same as a redline: a document showing the differences between two versions. The term is more common in transactional practice, particularly in securities filings, M&A agreements, and financial documents. When a client or opposing counsel asks for a "blackline," they want the same deliverable you would produce if they asked for a "redline": a marked-up document showing all changes between the agreed version and the current draft.
Do comparison tools produce redlines or blacklines?
Both. Every major comparison tool (Word Compare, Litera, Draftable, Clausul) produces the same type of output: a document showing insertions, deletions, and modifications between two versions. Whether you call that output a "redline" or a "blackline" is a labeling choice, not a technical one. The tool does not care which term you use. The output is the same regardless.
Is there ever a technical difference between a redline and a blackline?
In rare cases, some practitioners use "blackline" to mean a clean comparison (showing only what changed, without Track Changes metadata) and "redline" to mean a version with Track Changes markup still embedded. This distinction is not standard and varies by firm. If precision matters, ask the requester what format they want: "Do you want a Word document with Track Changes, or a clean comparison showing changes in marked text?" That eliminates ambiguity regardless of which term they used.