Yahoo is believed to be on the verge of selling its bookmarking service Delicious, possibly to the social "discovery engine" StumbleUpon, for a price believed to be around $1m (£619,000).

Delicious has been up for sale since it was revealed as being on a so-called "sunset" list of Yahoo's properties in mid-December, as part of an overarching review by chief executive Carol Bartz to try to focus only on profitable elements of the company that fit with its vision of being a content creator and means of carrying advertising. Delicious doesn't offer any way for Yahoo to sell adverts.

At the same time of the December announcement the handful of engineers who were developing the Delicious system are understood to have either been sacked or redeployed inside Yahoo, leaving only support staff.

Delicious has not revealed how many users it had at the time when Yahoo put it up for sale, but at the end of 2008 it had nearly 6m users.

StumbleUpon offers a similar bookmarking service to Delicious, and recently completed a $17m venture capital funding round.

Other bookmarking services, such as Pinboard, have seen a rapid influx of people migrating from Delicious because they fear their bookmarks will be lost when Yahoo closes the service. However in a posting a Delicious team member suggested that the API allowing third-party access to bookmarks will continue after any sale: "Feeds and API's are a key part of Delicious, and I would doubt that anyone would remove them from service, and we would certainly not want that to happen."

In a statement last week when rumours of the sale emerged, Yahoo said: "We are actively thinking about the future of Delicious and believe there is a home outside the company that would make more sense for the service, our users and our shareholders."

A report at Business Insider suggested the sale is taking some time to complete because Delicious's systems are reliant on Yahoo's infrastructure, and that it is being migrated on to third-party machines so that a sale can be wrapped up.

Yahoo acquired Delicious in December 2005 and is reckoned to have paid between $10m and $15m for it at the time. Delicious lets users bookmark web pages and share their bookmarks, including tags (such as "social" or "important" or "earthquake", or any combination of tags) for pages. That meant Delicious could generate a picture of what pages people thought had relevance to certain tags in real time. It was expected then that Yahoo would integrate the results into its search engine.

But the integration never happened to any extent. Josh Schachter, the founder of Delicious in late 2003, left the company in mid-2008, expressing dissatisfaction with Yahoo's use of the service.

Other properties that were on Yahoo's "sunset" list were Altavista, once one of the most popular search engines, MyBlogLog, Yahoo Bookmarks and Yahoo Picks.