The digital comics market crossed the $100 million sales threshold in 2014 (according to pop culture trade news site ICv2), and purchases from Amazon, following its acquisition of Comixology last year, could account for as much as 90% of it. Now the online giant is taking steps to protect its dominant position from rivals such as Apple, Google, and independent-minded publishers that prefer to support a variety of e-tailers.

Immediately following the acquisition, Comixology disabled in-app purchasing in iOS and Android, cutting out the 30% commission paid to the platforms. Though the move sparked some outrage from digital pundits, most customers rapidly adapted to making purchases through the website.

Consumers wanting in-app purchasing for new comics, however, still have options. They can buy through competing services such as iVerse ComicsPlus and Madefire, or buy single issues and collected editions directly from Apple and Google. Consumers can also buy through the publishers’ apps, most of which, until recently, used a “white label” implementation of Comixology’s platform—meaning that Comixology powers the back-end of many publisher branded apps—as the infrastructure for their storefronts. One advantage of buying comics directly from white-label publishers is that they also show up in customers’ Comixology libraries.

In June Amazon announced that Marvel had extended its exclusive distribution deal with Comixology (adding 12,000 periodicals to Amazon) for single issues, covering both the Comics by Comixology and Kindle reading platforms. Marvel dominates the single-issue market with a 41% dollar share and a 43% unit share, according to the most recent industry statistics. More importantly, Marvel comics are the gateway to merchandise and media franchises worth billions—something that Amazon certainly understands. The exclusive deal with Marvel is a major competitive advantage. It is hard to see how a competing comics distribution platform could be useful to Google or Apple without Marvel in its catalogue.

Closing the Back Door

In a less publicized move, Comixology has been winding up its white-label deals with second-tier publishers, driving them to look for other technical partners to support their branded apps. Customers can still buy comics from those publishers through Comixology’s storefront, and the company continues to support high-revenue branded apps from Marvel, DC, Image, and the Walking Dead.

Madefire has stepped into the void created by Comixology’s withdrawal from the white-label business, recently announcing new licensing terms for its motion-book platform and a deal to migrate the app of top-five publisher IDW from a Comixology back end to Madefire. Madefire CEO Ben Wolstenholme promises additional publisher announcements shortly. Wolstenholme said Madefire offers the service for fixed rates not linked to sales volume. That’s an attractive proposition to publishers suddenly in the market for a new digital distribution solution, and a serviceable model for Madefire, which has invested significantly in its motion-book technology platform.

Once the company has exhausted the relatively small pool of comics and illustrated-book publishers, who have established needs, Wolstenholme is banking on more speculative scenarios involving transmedia tie-ins with video games and films, and on new consumer technologies, such as virtual reality, to provide further growth. He said the company’s investors support this vision, but the new strategy may need some time in the market to pay off.

The technology shift has consequences for digital-comics customers. Purchases made through publisher apps powered by Madefire are no longer integrated with the popular Comics by Comixology app and vice versa. Readers who purchase through disparate channels will have to manage their collections in multiple libraries, which could irk fussy fans.

Comics from Madefire-powered publisher sites do connect to the Madefire storefront, but in three years of operation, Madefire has not demonstrated consistent sales traction despite significant promotional support from Apple. The metrics site App Annie shows the site’s gross book-category revenue rankings from iOS bouncing from the top 10 on its best days to troughs lower than 400 since January 2015.

Also according to App Annie, publisher apps other than DC, Marvel, and Image rarely generate significant amounts of money. Comixology, offering the same books at the same prices, outsells them more than 10 to one, despite the absence of in-app purchasing.

Given the low revenues and high complexity involved in maintaining publisher-branded comics apps, the retreat from white-label support could just be Comixology simplifying its operations to focus on other opportunities, it could be off-loading an underperforming business to a rival, it could be about perception, or it could be about control of the customer account. Whatever the reason, Amazon is giving publishers who need an independent channel a high-stakes three-way choice: (1) preserve account control and in-app purchasing but complicate the customer experience by moving to a Madefire platform, (2) invest in a standalone solution, or (3) give up trying to sell digital comics through branded apps altogether and consolidate through the Amazon/Comixology storefront.

Between this scenario and the Marvel exclusive, Amazon is leaving publishers and potential competitors an increasingly narrow path to market.

Correction: An earlier version of this story made a claim about the length of Comixology's contract extension with Marvel that is unverified and has been removed. The source of the size of digital comics marketplace is pop culture trade news site ICv2, which has been added.