REDMOND, Wash. – In Microsoft's expensive, decadelong battle against Google's search engine, no detail is too small.

Derrick Connell, a Microsoft vice president in charge of the engineering side of the 4,000-person team that builds the company's Bing Web search, takes work home with him every weekend.

Connell reviews lists of common queries people type into the search boxes at Google.com and Bing.com. In some, Bing displays more helpful results, he said. Others favor Google. Each is a battleground.

"We want to be the best," Connell said. "We believe in our technology."

How much the rest of the world believes in Bing is up for debate.

By one measure, the search engine now executes a record one out of every five searches made on desktop computers in the United States, a milestone Microsoft Chief Executive Satya Nadella touted last month in a meeting with Wall Street analysts. But Bing's standing internationally, and in fast-growing mobile search, is a fraction of that.

Still, executives and outside observers said Bing, launched six years ago, has gone from the butt of jokes to a tool comparable to Google in terms of its technology. Microsoft has integrated Bing's underlying data-crunching technology into its other software, and plans to tie it closely to its upcoming Windows 10 operating system.

Microsoft sites accounted for 8.4 percent of U.S. desktop search traffic when Bing debuted in 2009, well behind Google's 65 percent, according to comScore. In April, Bing's share had increased to 20.2 percent, gaining from Yahoo, Ask.com and AOL. Google's share has remained relatively steady.

Connell likes to put it this way: "Google was growing until we launched Bing."

The bottom line? The technology improved, said Danny Sullivan, founding editor of Search Engine Land. "Now, it's a credible alternative to Google."