Blacklining vs. Redlining: What Every Contract Professional Needs to Know

If you’ve ever asked a colleague whether to send a blackline vs. redline, you’ve probably heard two different answers. Most lawyers use a redline to show tracked edits inside a working draft, while a blackline compares two saved versions of a contract. 

Still, practitioners don’t all use the terms the same way, so this guide walks through both usages for transactional lawyers, in-house legal teams, and contract managers.

Key Takeaways

• A redline shows tracked edits in a draft, while a blackline compares two saved versions.
• Many lawyers use the terms interchangeably, but the difference matters for risk.
• Tracked changes only capture edits someone chose to track, so a blackline catches changes made with tracking off.
• AI contract review can speed up the first pass, and the lawyer decides which edits stay.

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What is Redlining?

Redlining means marking proposed changes directly in a working contract draft so every party in the negotiation can see each edit. The term “redline” comes from paper drafts, when lawyers marked edits in red ink so the changes stood out against the black text.

Microsoft Word’s Track Changes and Google Docs’ Suggesting mode both create redlines on screen, so you can redline in Word or redline in Google Docs with the same basic markup. Both tools show inserted text in color and strikethrough text for deletions, while margin comments flag points the parties still need to discuss.

A redline doubles as an audit trail for the negotiation because the software logs who made each change and when. Still, a redline only shows the edits someone chose to track, which is where blacklines come in.

How Redlining Works in Practice

Say the counterparty’s in-house counsel sends an NDA with a confidentiality clause that covers everything your client shares. 

You turn on Track Changes, narrow the clause to information marked confidential, and leave a margin comment explaining why the original reached too far. When the draft goes back, Word shows who changed what and when, so both sides can follow the edit history.

Lawyers redline a contract by editing with Track Changes on and explaining each substantive change in a margin comment, though the record has one limit. A redline only captures what someone changed while tracking was on, so anything edited with it off never shows up.

What is Blacklining?

Blacklining compares two versions of a document and shows every difference between them, whether or not anyone tracked the changes along the way.

The term “blackline” traces back to comparison reports, which lawyers ran to check one draft against the next. Word’s Compare feature produces what Microsoft calls a legal blackline, and high-volume contract teams often add dedicated document comparison tools. Word leaves both drafts untouched and produces a third document that marks each difference as a tracked change.

In other words, a blackline shows the net difference between two points in time, so it can’t tell you who made each change or why. That trade-off pays off, though.

A redline can hide edits someone accepted or stripped out between rounds, according to guidance from one legal software vendor. A blackline closes that gap because it compares both versions directly and gives you a full record of what changed.

How Blacklining Works in Practice

Now say the counterparty sends the NDA back as a clean copy with no visible markup and a note that everything’s agreed. 

Before anyone signs, you run Word’s Compare feature against the last agreed draft. The blackline shows your narrowed confidentiality clause intact, but it also flags a new non-solicitation provision and a shorter notice period that nobody mentioned. 

A blackline works as a safety net because it catches untracked changes before they make it into a signed contract.

Do Lawyers Actually Use These Terms Differently?

The terms “redline” and “blackline” mean the same document to some lawyers and two different documents to others.

In the first camp, either word just means a contract with the edits showing, so a partner asking for “the redline” and another asking for “the blackline” may want the same file. The confusion isn’t new, either. None of the lawyers consulted for a 2007 Word guide had heard of Microsoft’s “legal blackline” label, though they all knew redlining.

In the second camp, a redline means tracked edits inside a working draft, and a blackline means a comparison of two saved versions. This guide follows the second camp’s distinction because many practitioners and software guides use it, and Microsoft even calls its Compare tool a legal blackline.

So when opposing counsel or a counterparty says “send me a blackline,” ask one question before you reply. Do they want a comparison, and if so, against which version? Confirming the convention with opposing counsel keeps you from sending the wrong file mid-negotiation.

Blacklining vs. Redlining: Key Differences and When to Use Each

A redline tracks live edits inside one working document, while a blackline compares two separate versions and shows every difference between them.

Here’s a side-by-side comparison.

Redlines and blacklines work together, because a redline tells the story of how the deal moved, while a blackline confirms where it landed. Most teams use both, often on the same contract.

Redlining fits the drafting and negotiation stages of the contract lifecycle, while blacklining fits the pre-signature and post-execution stages. During drafting, the party that receives the first draft usually prepares the opening round of redlines, so every proposed change stays visible from day one.

As negotiation continues, both sides keep trading redlines and margin comments until they settle each open point. Word’s Lock Tracking feature requires a password before anyone can turn off Track Changes, keeping every edit in the record.

The pre-signature stage carries a quieter risk. A contract’s text may no longer match what the parties negotiated by the time it reaches signature, as one legal software vendor warns. A blackline against the last agreed draft, run right before anyone signs, catches that drift.

After execution, or during due diligence, a blackline of each signed contract against your standard template shows exactly where the final terms drifted from your playbook. A template blackline helps in-house counsel and contract managers spot nonstandard clauses across a whole contract portfolio.

How AI Contract Review Fits in

AI contract review speeds up the first pass by flagging risks and suggesting redlines, while the lawyer still decides which changes to accept.

AI contract review tools check a contract against your team’s playbook and flag clauses that carry unusual risk. They then suggest alternative language inside the working document, so the lawyer reviews each suggestion right where the negotiation is happening. Contract-specific tools center on how clauses fit together and what the market usually accepts, so their suggestions stay tied to contract work.

That second pair of eyes matters more than most teams assume.

The 3,019 contracts in the Spellbook Labs study were executed agreements that had already passed through drafting, negotiation, and signature, which shows how easily drafting issues slip past manual review.

Spellbook is a contract platform that adds suggested redlines and comments in Microsoft Word and Google Docs under the lawyer’s name. The lawyer then chooses which Spellbook suggestions to approve and apply.

Spellbook handles the first pass of contract review, and the lawyer keeps the final say. Document comparison still does a separate job, though, because a blackline confirms what changed between versions after the review rounds wrap up.

See How Spellbook Streamlines Contract Review

Spellbook helps lawyers move through contract review faster, whether you’re redlining a first draft or giving a final version one more look. Spellbook suggests redlines right inside Microsoft Word and Google Docs, and Spellbook Playbooks flag clauses that fall outside your team’s standards. The lawyer approves every change before it reaches the counterparty.

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Frequently Asked Questions

What is the difference between redlining and blacklining?

A redline tracks edits inside a working draft. A blackline compares two saved versions and shows every difference between them. Redlines suit live negotiation, while blacklines suit verification later in the deal. Still, some lawyers use the two words interchangeably, so it’s worth confirming which one the other side means.

Can you convert a redline into a blackline?

Yes, Word’s Compare feature turns a redline into a blackline once you accept the tracked changes and compare that clean version against the original. Word even offers to accept leftover tracked changes first. Lawyers often do this before signature, since the comparison confirms the final document includes only the agreed edits.

When should I use blacklining instead of redlining?

A blackline works better than a redline when a document comes back without visible markup, and you need to see what changed. Blacklining fits pre-signature review, due diligence on executed contracts, and any version the counterparty returned without Track Changes. In each case, a blackline catches edits that a redline would never show.

Is blacklining the same as document comparison?

Blacklining is one form of document comparison, and many lawyers use the two terms interchangeably. In Microsoft Word, you create one with the Compare feature, and the output may be called a blackline, a comparison document, or a legal blackline, which is Microsoft’s own label.

Can AI tools redline contracts automatically?

Yes, AI contract review tools suggest redlines automatically by checking a contract against your team’s playbook and flagging clauses that fall outside it. Even so, the lawyer should review every suggested edit before it reaches a counterparty. Spellbook, for example, adds suggested redlines in Microsoft Word and Google Docs, and the lawyer chooses which ones to approve.