Chart of the Day · SEP 18, 2026

Anthropic SDK vs. OpenAI SDK: npm Downloads

In 46 weeks the Anthropic SDK went from 34% to 97% of the OpenAI SDK's npm downloads. Developer distribution can be won late, and lost fast.

Mode VC ·

The signal

Anthropic's SDK went from 34% to 97% of the OpenAI SDK's weekly npm downloads in 46 weeks. It passed OpenAI in one week (25 May).

Weekly npm downloads of the official JavaScript SDKs (@anthropic-ai/sdk, openai, @google/genai), complete Monday–Sunday weeks, 6 Oct 2025 – 30 Aug 2026.

Anthropic (@anthropic-ai/sdk)OpenAI (openai)Google (@google/genai)
Sources: npm registry downloads API · Official launch posts (launch feed, captured 7 Oct 2026)MODE VC

Downloads count installs, including CI runs, mirrors and packages that depend on an SDK; they are not people or API spend. The npm API returns 0 on some days; we treat those as gaps and drop any week with a gap. That is why the line stops at the week of 24 Aug: the API returned 0 on 3 Sep, 7 Sep, 8 Sep and 15 Sep. Week-to-week moves of a few points are noise.

Show the data (43 rows)
Week ofAnthropicOpenAIGoogleAnthropic as % of OpenAI
6 Oct 20252.5M7.3M1.9M34%
13 Oct 20252.5M7.5M2.2M34%
20 Oct 20252.7M7.4M1.6M36%
27 Oct 20252.6M7.3M1.6M36%
3 Nov 20252.7M7.7M1.7M36%
10 Nov 20252.8M7.7M1.8M37%
17 Nov 20253.1M8.1M2.1M39%
24 Nov 20252.8M7.3M2.0M38%
1 Dec 20253.4M8.8M2.3M38%
8 Dec 20253.4M8.7M2.4M39%
15 Dec 20253.3M8.5M2.6M38%
22 Dec 20252.2M5.3M2.0M42%
29 Dec 20252.2M5.3M2.1M43%
5 Jan 20263.5M8.8M3.3M40%
12 Jan 20263.7M9.6M3.4M39%
19 Jan 20264.1M10.4M3.7M40%
26 Jan 20265.2M11.9M4.6M44%
2 Feb 20265.7M12.2M4.9M47%
9 Feb 20265.8M12.4M5.7M47%
16 Feb 20265.8M11.9M5.8M49%
23 Feb 20266.9M13.8M8.1M50%
2 Mar 20267.7M14.9M8.8M51%
9 Mar 20268.8M16.8M9.8M52%
16 Mar 20269.1M16.4M9.3M55%
23 Mar 202610.4M16.4M9.1M64%
30 Mar 202612.4M15.7M9.1M79%
6 Apr 202613.4M17.1M9.6M78%
13 Apr 202614.8M17.9M10.2M82%
20 Apr 202615.4M19.3M10.6M80%
27 Apr 202618.4M21.1M11.2M87%
4 May 202617.1M20.5M10.4M83%
11 May 202617.9M21.6M10.9M83%
18 May 202619.5M22.5M11.9M87%
25 May 202624.4M24.0M13.5M102%
8 Jun 202623.5M25.8M15.9M91%
15 Jun 202624.4M27.4M17.0M89%
29 Jun 202623.1M25.4M15.3M91%
13 Jul 202627.1M29.5M16.2M92%
20 Jul 202627.6M30.6M16.4M90%
27 Jul 202629.7M32.7M17.8M91%
3 Aug 202629.8M32.0M17.5M93%
17 Aug 202633.9M34.5M21.2M98%
24 Aug 202638.7M39.7M23.4M97%

The Mode read

In the first days of September, Anthropic, Google and OpenAI each shipped new models. For a JavaScript developer, the first step with any of them is the same: install the lab's SDK. So whose SDK do developers install?

In the week of 6 Oct 2025 the Anthropic SDK had 34% of the OpenAI SDK's npm downloads. In the week of 24 Aug it had 97%, and in the week of 25 May it was ahead. Anthropic grew 15.5× in that time, OpenAI 5.5× and Google 12.2×. The catch-up was not smooth: 57% of it came in eight weeks, from 2 Mar to 27 Apr.

Developer defaults look locked until they move, and then they move in one quarter. That cuts both ways for founders who sell to developers. A second-place tool can take the default with a burst of better product and presence where developers start a project. A leader can lose it just as fast. Track your installs as a share of the leader's, every week; your own total can rise while the default slips away.

Developer defaults do not drift. They flip, often inside one quarter.

What we would back: Developer tools that are taking the default from a category leader, visible week by week in install share.