A blackline document is a separate comparison file that shows every difference between two versions of the same text, with deletions, additions, and unchanged content each marked distinctly. It isn’t the edited document itself. It’s a third file, generated after the fact, that lets you see at a glance exactly what changed between version A and version B. Blacklines show up constantly in contract negotiations, SEC filings, and any situation where one party needs to verify what the other side altered.
Blackline, Redline, and Track Changes Are Not the Same Thing
These three terms get used interchangeably, but they describe different things, and the distinction matters when someone asks you for one and means something specific.
A redline is what you see during active collaboration. When two parties are negotiating a contract and trading drafts, the marked-up working copy with everyone’s edits and comments visible is the redline. Turning on Track Changes in Microsoft Word produces what most people would call a redline: every insertion, deletion, and comment appears in colored markup while the document is still being worked on.
A blackline is retrospective. It compares two documents, usually an earlier version and a later one, and generates a clean output showing only the net differences. The back-and-forth revision history is stripped out. What you get is the bottom line: what moved between the two versions. In Word, the Compare Documents or Legal Blackline feature produces this as a new third document, leaving both source files untouched.1Microsoft Support. Compare Document Differences Using the Legal Blackline Option
Track Changes is a software feature, not a document type. It’s the mechanism Word uses to record edits in real time. Track Changes produces redlines. The Legal Blackline tool produces blacklines. One is live and collaborative; the other is comparative and after the fact.
How to Create a Blackline Document in Microsoft Word
Word’s built-in comparison tool handles most blackline needs without any add-on software.
- Open Word and go to the Review tab. In the Compare group, select Compare, then choose “Compare two versions of a document (legal blackline).”
- Browse for the earlier file under “Original document” and the newer file under “Revised document.”
- Choose your comparison options. You can tell Word whether to compare comments, formatting, text changes, or all of the above, and whether to display differences at the character or word level.
- Click OK. If either document contains existing tracked changes, Word will prompt you to accept them before running the comparison.
Word then generates a new third document showing every difference as tracked changes. The two source files remain completely unaltered.1Microsoft Support. Compare Document Differences Using the Legal Blackline Option Deleted text typically appears with strikethrough formatting, new text appears underlined or in a contrasting color, and unchanged text stays in standard black.
When Word’s Tool Isn’t Enough
For firms producing blacklines regularly, Word’s built-in feature has real limits. It only compares Word documents, it can miss changes inside tables and images, and it doesn’t handle PDFs at all. Dedicated comparison software such as Litera Compare works across Word, Excel, PDF, and PowerPoint, catches formatting changes Word overlooks, and can apply optical character recognition to scanned PDFs. Some of these platforms now add AI-powered analysis that summarizes changes and flags potential risks in a revised contract. Whether the cost is worth it depends on volume. A solo practitioner comparing a few contracts a month probably doesn’t need it. A firm processing hundreds of amended filings usually does.
Where Blackline Documents Are Used
In legal practice, blacklines are close to indispensable. When opposing counsel returns a signed contract, a blackline against the last agreed draft immediately reveals whether any language was altered. In transactional work such as mergers, real estate closings, and loan agreements, multiple rounds of revision are the norm, and a blackline of each round keeps everyone honest about what moved between drafts.
In securities work, blacklines play a regulatory role. When a company amends a registration statement filed with the SEC, the marked copy must clearly indicate every change from the prior version. The same principle applies to amended prospectuses, annual reports, and other disclosure documents where regulators need to see precisely what was revised.
SEC Filings
The governing regulation requires that marked copies of amendments “indicate clearly and precisely … the changes effected in the registration statement by the amendment,” whether through underlining or another method that makes each change obvious.2eCFR. 17 CFR 230.472 – Filing of Amendments; Number of Copies On EDGAR, filers typically tag changed text with specific markup codes to serve as the blacklined version. The SEC has also indicated it will accept emailed marked copies in a more reader-friendly format for filings under active staff review.3SEC.gov. ADI 2018-04 – Marked Copies of Amendments to Registration Statements
Court Filings
Federal Rule of Civil Procedure 15, which governs when and how parties can amend pleadings, does not itself specify formatting requirements for showing the changes.4Legal Information Institute (LII) / Cornell Law School. Federal Rules of Civil Procedure Rule 15 – Amended and Supplemental Pleadings That falls to local court rules, and many federal district courts require parties seeking to amend a pleading to submit both a clean copy and a redlined or blacklined version showing all differences from the original. If you’re filing an amended complaint or motion in federal court, check the local rules. There’s a good chance a blackline will be required as an exhibit.
Why Lawyers Run Blacklines on Documents They Receive Back
Blacklines aren’t only a convenience. They’re tied to the ethics rules that govern how lawyers handle revisions. The ABA’s Model Rules of Professional Conduct, adopted in some form by every state, establish two relevant standards. A lawyer cannot knowingly make a false statement of material fact to another person during the course of representation.5American Bar Association. Rule 4.1: Truthfulness in Statements to Others And a lawyer must not engage in conduct involving dishonesty, fraud, deceit, or misrepresentation.6American Bar Association. Rule 8.4: Misconduct
Ethics opinions have consistently held that substantive changes to a document from the other side must be explicitly disclosed. Making a material change to a document submitted by opposing counsel and returning it signed without saying so can be treated as professional misconduct. This is the exact scenario a blackline is built to catch: a returned document that looks the same at first glance but contains alterations buried in the text. Running a comparison before signing anything you receive back is one of the simplest protective habits in practice.
Clean the Metadata Before You Send
Blackline and redlined documents can carry hidden metadata that reveals far more than you intended to share. Track changes, comments, author names, editing timestamps, file paths, previous document versions, and text formatted as hidden can all travel with a Word file when you send it to the other side. If you built the document from an older file, client-specific information from the original may still be embedded.
Before sending any comparison document externally, run Word’s Document Inspector to find and strip hidden data.
- Save a copy of the file first. Document Inspector’s removals can’t always be undone.
- Go to File, then Info. Select “Check for Issues” and choose “Inspect Document.”
- Select what to inspect. Comments, revisions, document properties, personal information, hidden text, and custom XML data are all options.
- Review the results and click “Remove All” for any category you want cleaned.
The Inspector can strip comments, revision marks, version information, author names, template metadata, email headers, and hidden text in one pass.7Microsoft Support. Remove Hidden Data and Personal Information by Inspecting Documents, Presentations, or Workbooks Converting the final document to PDF or plain text before sharing removes another layer of risk, since those formats store far less metadata than native Word files. The extra two minutes is worth it. A metadata leak during a negotiation can undermine your position on its own.