Arc, The Washington Post’s publishing software, continues its slow march towards becoming the go-to content management system for news organizations, from modest alt-weeklies to multi-paper chains.

This week, the Philadelphia Media Network announced that it would be moving to Arc for all of Philly.com’s publishing needs, working directly with the Post team to test new Arc tools and features throughout the year-long transition process. The nonprofit Lenfest Institute, which owns PMN, will document the process in a series of white papers for the other metro news organizations participating in the Knight-Lenfest Newsroom Initiative, laying out details on why it chose to adopt Arc in the first place and how the transition worked, intended to guide other publishers that are considering a new CMS for their digital operations.

“Our transition from the system we use now to Arc coincides, and times, well with our current newsroom transformation overall, which is focused around digital change,” Tian Chen, chief product officer at PMN, said. Though PMN might’ve had the technical staff to pull off some website and backend improvements itself, “the amount of effort we’d have to invest into doing these things is completely outweighed by effort it would take for us to just do it with Arc.”

The newsroom will start by switching over core content creation tools first, such as ones for composing articles and scheduling, Chen told me, and by the fall of this year hopes to start using other tools in the Arc suite, such as its A/B testing feature and new digital advertising tools. Philly.com gets around 6.9 million unique visitors per month according to comScore — 5.8 million from mobile — and wants to grow the audience base, so improving user experience on its platforms is critical. The site also launched a metered paywall this past fall; the Arc team is building out a more easily customizable subscription tools for publishers, which PMN will also help test.

“The goal is to have a very productive and transparent commercial relationship, underpinned by a journalistic mission,” Jim Friedlich, the institute’s executive director, said. “It is also a harbinger of future such deals in local news — smart publishers playing at scale on strong platforms and no longer building their own.”

Friedlich recalls that he’d been in touch with both The Philadelphia Inquirer and Washington Post CIO Shailesh Prakash more than two years ago, before the formation of the Lenfest Institute, but that a very circumspect Arc team felt then it wasn’t ready to handle more widespread commercial usage. PMN’s transition efforts are supported by $400,000 from the Lenfest Institute to cover the one-time project costs of transitioning to the Arc publishing system, but PMN itself will take on the remaining continued operating costs of Arc after it’s switched over. (The initial funding comes out of the $1 million the Lenfest Institute gave last fall to PMN for technical overhauls and improving its reporting resources, as part of a large infusion of grants to local news projects).

Arc Publishing has “dozens” of other customers — the Post wouldn’t share an exact number — all of whom can work with the Arc team on site presentation technical transition, troubleshooting, and new features (the PMN arrangement is unique in that the Lenfest Institute will share lessons learned throughout the transition). Arc handles all the hosting through Amazon Web Services, and charges commercial clients based on each publisher’s site traffic. $10,000 per month is the publicly cited figure for the smallest Arc users, up to around $150,000 per month for the larger publishers. Most Arc clients so far have been medium to large-sized publishers, director of Arc Publishing Matt Monahan told me. (College newspapers such as Columbia’s Spectator and the University of Maryland’s Diamondback were the first to test Arc, for free.) The Post declined to share revenue figures for Arc’s business, but revenue “doubled year-over-year,” according to a November Fast Company article.

The Post has previously said Arc is moving towards being able to offer a completely automated, self-service option, though it’s not quite there yet (parts of deployment are starting to be automated, and certain developments, like a ticketing system for troubleshooting, set it on a path to scaling faster). In the past two or so years, Arc has been adding publishing clients at a fast trickle, but slowly enough that it can still be responsive to individual publishers’ requests.

The Argentina-based digital-only news site Infobae was among its earlier clients. Arc deals only with digital publishing, but can integrate with news organizations’ print systems. Canada’s Globe and Mail is a client. So are the Tronc papers, such as the Los Angeles Times and the Chicago Tribune. McClatchy, which is currently using a different CMS, has looked at adopting Arc for its papers (though “through our normal course of business we continuously look at a wide range of CMS solutions including Arc,” its VP for product and tech Scott Manuel told me over email). The Portland alt-weekly Willamette Week was Arc’s first commercial client, and its sister alt-weekly the Santa Fe Reporter flipped the switch on its new Arc-powered website last October. (Its other sibling, Raleigh Durham’s Indy Week, isn’t using Arc.)

Santa Fe Reporter is on the tiny side of the spectrum of Arc clients. Its New Mexico newsroom has a staff of 14 and the alt-weekly serves a market of around 90,000 people and gets around 30,000 pageviews to its site each week, about a quarter of it direct, according to publisher and editor Julie Ann Grimm. (It also distributes 15,000 free print issues every Wednesday.) It also doesn’t have any coding staff in-house to help speed along technical tweaks.

“When we started working in earnest with their team, we had very clear vision of our site,” Grimm said. “In the process, we had a lot of back-and-forth with their developers, helping them understand how we wanted their product to work for us, and looking at how far you could stretch certain tools and features. Early on, our art director drew up some wireframes of what our ideal website might look and feel like. If you look at those wireframes from two years ago now, I think we got there.”

Some styling and layout details Grimm said she wishes SF Reporter could have more control over. But transitioning to Arc has offered major benefits not necessarily visible to readers.

“Changing to the Arc system allowed us to reinvent our whole newsroom workflow. We were using various patched systems. Google Docs, Microsoft Word, our copyeditors were emailing things back to our reporters,” Grimm said. “Now we use their system for content generation, and use Arc to flow through the whole copyediting process. We can export to an RTF for InDesign for our print edition. That’s made a difference for us as well. It’s been a big change in our culture.”

She also credited the Arc team for the clean migration of the Reporter’s years of archives.

“They were helping us move all of our stories from when we first really went online, pulling all the data around the ways we built each story and feeding it into the new system,” she said. “So how the images show up, how the links to other stories would show up, how the subheads would display — all of these were problems we had to work through. Today, if you find an older article, you’ll see it pretty much has the same functionality our newer articles do, even though it came from an older system. That’s really worth something to us. Our stories that go back in time are just as valuable.” (The Reporter staff did its own tagging.)

Infobae adopted Arc systems 20 months ago when it was still “pretty experimental,” Infobae product director Pablo Mancini said. The 16-year-old site has more than 100 staff throughout Latin America, as well as correspondents across the U.S. Since moving to Arc systems, it’s doubled its audience to 42 million monthly unique visitors.

“I’ve been working in this field for 15 years, and I really think their CMS is a game changer,” he said. “We use Ellipsis, for multiple people creating and publishing stories. PageBuilder, their core tool for managing the homepage, is really impressive. They have templates for AMP. Goldfish, their video management system, we’ve used from the beginning, and it’s very powerful.

“They have a lot of tools that can help you grow your site, but in my view the value is in being able to work with their engineering team to implement features relatively quickly.”

The full Arc suite includes all the usual publishing tools, but also available to other publishers are many features first tested in the Post newsroom. The Post itself is in the final stages of transitioning entirely to using Arc, Monahan told me: “A lot of this was built here, for problems we saw inside our own business, so the goal is, by the time we get through this year, the way you see the system running at the Post will be indistinguishable from how our clients use it.”

Building up revenue-side tools are a top priority for the Arc team this year, including products around digital advertising, and importantly, a digital subscriptions platform for handling different types of paywalls (“we should be in place with beta partners for this in Q2,” Monahan said).

“You have clients like The Globe and Mail, which has a combination of metered access and restricted premium content. You see the paywall model we have at The Washington Post. We’ll have something that can support all these models — a configurable paywall where publishers can change a lot of the settings for,” Monahan said. “The learnings from what we’ve done with our own subscriptions business in the past year are informing features we’re building into this tool.”

Another big consideration for Arc will be how to handle its larger clients — particularly companies that own multiple distinct news sites.

“You’re seeing a lot of consolidation, with newspaper chains. There are specific capabilities you need when you’re running multiple sites, or even a single site with multiple different verticals, such as content restrictions, different permissions for staff,” Monahan said. “That’s another big thing for the next few months.”