Jewelry.com’s desktop site was a thick 10.07 megabytes between July 17-30.

But a heavy mobile site doesn’t mean it has to load slowly. Jewelry.com, operated by Richline Digital, No. 92 in the Internet Retailer 2017 Top 500, loaded on average in 4.07 seconds during the two-week time period, which is only a touch slower than the average web speed on this month’s Desktop Performance Index.

The index monitored Internet Retailer’s Top 100 retailers’ desktop home pages between July 17-30, according to data provided by digital performance analytics company Catchpoint Systems Inc. Catchpoint provides Internet Retailer with two monthly site performance indexes, one for mobile sites and one for desktop sites.

Jewelry.com ranked No. 59 on the index. However, considering the site is three times heavier than the index average of 2.95 megabytes, the retailer’s performance is strong, a Catchpoint spokesman says.

“The website loads most of its Javascript files and images after more critical elements, indicating to users that the site has loaded. This is the key reason why this site’s performance is stronger than other heavy sites like Shop.com (No. 66 in the Top 500) and CDW Corp. (No. 14),” the spokesman says.

At the top of the index, 1-800 Contacts Inc. (No. 93 in the Top 500) reached No. 3, up from No. 5 last week, and Walgreen Co. (No. 39) maintained its No. 1 spot and is the only retailer with a less than 1 second load time. Here are the top 10 performers:

For the two weeks of July 17-30, the Top 100 retailers’ average load time was 3.71 seconds compared with 3.63 seconds the previous month. The 100 leading North American retail sites are those ranked by Internet Retailer by online sales in 2016, according to Internet Retailer’s Top500Guide.com.

The average page weight  during the two-week period was 2.95 megabytes compared with 2.77 megabytes the previous month, and the average number of hosts was 50 compared with 48. The average number of items per page was 175 compared with 172 the previous month. The 100 sites were, on average, 99.91% available July 17-30, compared with 99.95% available between June 19-July 2.

Catchpoint monitors each website’s home page with measurements taken from Catchpoint’s in-country or in-region monitoring nodes, at intervals of five minutes for two weeks each month. Backbone monitoring nodes are the locations of Catchpoint’s devices that are near data centers operated by the main internet service providers that provide service to a city. The nodes simulate end-user contact with each website. Catchpoint monitors web page load time, availability, hosts and items.

They are defined as follows:

Web page load time: The time it takes for enough page elements to load for a consumer to begin interacting with a page, such as searching, tapping or scrolling. From a consumer point of view, the time it takes for the progress bar or spinning wheel to stop.

Availability: The percentage of time during the two-week test period that the site can be successfully reached by a consumer.

Host: Any domain that delivers data, content or services over the internet to the site.

Items or Requests: Web page components, such as files or images that a page loads from internal and external hosts or domains. These can include PDFs, PNGs, JPEGs and GIFs.