Patents

i4i v. Microsoft: How a Tailored Injunction Survived eBay and Forced Word to Change

The Federal Circuit affirmed a permanent injunction against a feature of Microsoft Word, showing how a small patentee can satisfy all four eBay factors against a dominant competitor when the injunction is carefully scoped.

July 21, 2025
A laptop displaying a word-processing document on a desk
The injunction reached a custom XML editing feature inside Microsoft Word. Shutterstock
Educational content, not legal advice. This article explains general legal concepts. It does not create an attorney–client relationship. For your specific situation, consult a licensed attorney.

Three years after eBay ended the automatic patent injunction, the Federal Circuit confronted a hard test of the new equitable regime: could a small Canadian software company obtain a permanent injunction against a feature buried inside Microsoft Word, one of the most widely used programs in the world? In i4i Limited Partnership v. Microsoft Corp., 598 F.3d 831 (Fed. Cir. 2010), Docket No. 2009-1504, the court answered yes. The decision is a leading illustration of how the four eBay factors actually play out when a practicing patentee squares off against a much larger infringer — and of how careful tailoring can save an injunction from being too disruptive to issue.

At a glance

  • Case: i4i Limited Partnership v. Microsoft Corp., 598 F.3d 831 (Fed. Cir. 2010), Docket No. 2009-1504
  • Court: U.S. Court of Appeals for the Federal Circuit (panel: Judges Schall, Prost, and Moore; opinion by Judge Prost)
  • Decided: December 22, 2009; revised opinion issued March 10, 2010
  • Holding: The district court did not abuse its discretion in granting a permanent injunction against the infringing custom-XML feature of Microsoft Word; all four eBay factors supported relief, though the injunction’s effective date was modified from 60 days to five months
  • Note: A separate appeal to the Supreme Court concerned only the clear-and-convincing standard for proving invalidity; the injunction analysis discussed here is the Federal Circuit’s

The verdict and the injunction

i4i owned a patent directed to a method of editing documents containing markup languages such as XML, separating a document’s content from its structure (its “metacodes”). i4i contended that the custom-XML editor in certain versions of Microsoft Word practiced its claimed method. After a seven-day trial in the Eastern District of Texas, the jury found the patent valid and willfully infringed and awarded i4i roughly $200 million. The district court added enhanced damages and granted a permanent injunction barring Microsoft from selling versions of Word with the infringing custom-XML capability.

Microsoft appealed nearly everything — claim construction, infringement, validity, damages, and the injunction. On the injunction, the Federal Circuit applied eBay factor by factor and affirmed, supplying a model of how the equitable test operates when the patentee competes, however modestly, with the infringer.

The four factors, applied

Irreparable injury. The court accepted the finding that i4i had suffered harm that money could not readily repair. i4i and Microsoft competed in the market for XML editing tools, and the infringement had eroded i4i’s market share and threatened to render its products obsolete as customers gravitated to the functionality built into Word. Lost market share, lost business opportunities, and the erosion of a small company’s position against a dominant incumbent are classic forms of irreparable harm precisely because they are difficult to quantify and to undo.

Inadequacy of legal remedies. The same difficulty that made the harm irreparable made damages inadequate. The court recognized the practical problem of compensating, in dollars, the loss of customer relationships, brand recognition, and competitive standing that follows when a dominant product absorbs a smaller rival’s distinctive feature. Damages could redress past infringement; they could not restore i4i’s position going forward.

Balance of hardships. This factor crystallized the analysis. The infringing custom-XML capability was, in the court’s framing, but one of “thousands” of features in Word. To Microsoft, losing it meant disabling a single, non-core function. To i4i, the feature was central to its entire business. That asymmetry — peripheral to the infringer, existential to the patentee — weighed heavily in favor of relief.

Public interest. The court was attentive to the disruption an injunction against a ubiquitous product could cause. But the injunction had been narrowly drawn: it did not require Microsoft to recall or disable existing installations and did not bar Word itself, only the infringing custom-XML functionality in future copies. So scoped, the injunction protected i4i’s patent rights without depriving the public of the word processor on which it relied.

Tailoring and timing: the modified effective date

The most instructive feature of the decision is the court’s willingness to adjust rather than vacate the relief. The district court had ordered Microsoft to comply within 60 days. The Federal Circuit found that timetable unsupported: the only record evidence on how long it would take Microsoft to remove the infringing feature and ship compliant versions indicated it needed at least five months. Because nothing in the record justified the shorter period, the court modified the injunction’s effective date to roughly five months out.

That modification is a quiet but important lesson. Under eBay, the equitable inquiry does not end with whether to enjoin; it extends to how — scope, carve-outs, and timing. An injunction can be both granted and engineered to minimize collateral disruption, and an appellate court reviewing for abuse of discretion may recalibrate the implementation without disturbing the underlying entitlement to relief.

Open questions

i4i shows the four factors converging in a patentee’s favor, but it leaves the harder variations unresolved. How small can a patentee’s market presence be before “competition” no longer supports a finding of irreparable harm — does any market overlap suffice, or must the patentee show meaningful, attributable losses? When the infringing feature is one of thousands, the balance of hardships favored i4i, but the same arithmetic could be turned against a patentee whose contribution is genuinely marginal to its own business. And how far may a court go in re-drawing an injunction’s scope and schedule before it has effectively substituted a compulsory license for equitable relief? These questions recur whenever a component patent meets a complex product.

Implications

  • Practicing patentees can win injunctions against giants. Size disparity does not defeat relief; a small competitor that shows lost market share and obsolescence risk can satisfy eBay.
  • Scope is strategy. A narrowly drawn injunction — sparing existing users and targeting only the infringing feature — is far more likely to survive the public-interest factor.
  • The balance of hardships cuts both ways. That an infringing feature is minor to the defendant can favor the patentee (low hardship to enjoin) even as it cautions against injunctions where the feature is also marginal to the patentee.
  • Timing is reviewable. Compliance deadlines must be grounded in record evidence; an unsupported, aggressive deadline can be modified on appeal.
  • A blueprint for component cases. i4i remains a frequently cited template for how to seek — and how to grant — injunctive relief against a single feature of a multi-feature product.

Frequently asked questions

Did Microsoft have to pull Word off the market? No. The injunction reached only the infringing custom-XML functionality in copies sold after the effective date and expressly did not disable the feature for existing users, so Word itself remained available.

Why did the court change the injunction’s deadline? The district court’s 60-day compliance window was not supported by the evidence. The only proof of how long removal would take pointed to at least five months, so the Federal Circuit modified the effective date accordingly.

Is this the same i4i case the Supreme Court decided? It is the same litigation, but a different question. The Supreme Court’s later decision addressed the burden of proof for invalidity (clear and convincing evidence). The injunction analysis described here is the Federal Circuit’s.

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