Add HTTP/3 SQL query

[tunetheweb]

HTTP/3 is here! Well QUIC is and HTTP/3 is not far behind. We've already noticed HTTP/2 dropping because of this so think we should add an HTTP/3 graph, so adding the query is the first part of this.

There's a few complexities to consider compared to the equivalent HTTP/2 graph:

The HTTP/2 query is ridiculously expensive (see #110 ). I've gone for the cheaper suggestion for HTTP/3 since we don't need that historical data when the data was wrong. It's not quite as cheap as the HTTP/2 suggestion as need to look at alt-svc response header (for reasons I'll discuss below), but still it's only $15 as opposed to $1,000+.

HTTP/3 has been around for a while in pre-release versions and arguably Google's QUIC could be included in this going back nearly 10 years. However I've decided to limit this to HTTP/3 (aka h3), however I have included the last draft version (h3-29) as that is what will become HTTP/3 as soon as the IETF signs of the RFCs — so it is HTTP/3 in all but name. It is also what is being used now, and so explains the offset from HTTP/2 dropping, whereas waiting for h3 will show a delay between that drop, and this ramp up. That h3-29 version started appearing from June 2020 so the graph will start before HTTP/3 officially exists but think that's OK. This sheet ran the query for a few combinations and current usage is from 0% (pure HTTP/3 or h3), 9-10% (HTTP/3, h3 or h3-29), slightly higher 9-10% for all versions of h3, and 11.5% if we also include Google's QUIC. So I think the second option is the right one.

HTTP/3 will often not be used by our crawl. This is because, by default the browser uses TCP and then receives an alt-svc header saying "hey I support HTTP/3, so next time you're talking to me why not use that." If it needs to open another connection (e.g. an uncredentialled connection for Fetch or the like) then it might use HTTP/3, but it's not gonna be consistent. This is different to HTTP/2 where it's negotiated as part of HTTPS so should be used if supported. So, rather than measure HTTP/3 usage, I've decided to measure HTTP/3 support by looking at protocol used OR alt-svc support. Got some support online for this approach. Will need to add an explanation to the chart when we add this to the site to explain this difference from HTTP/2 and how it may double count usage in both HTTP/2 and HTTP/3 chart for some sites but think it's the right measure.

[rmarx]

I do think this is the correct approach.

Some further thoughts:

• h3 is already "officially" in use today. Even though the RFC hasn't landed, the IETF decided to just start deploying h3 together with QUIC v1 (RFC9000 and siblings). Most big deployments today do both h3 and h3-29 IIUC, the latter primarily to support older clients (e.g., mainline version of Safari only does h3-29 for now). It's a small nit, but somewhat important :)

• If query cost is the problem, then I don't think it'd be such a big problem to cut down the logic to just checking alt-svc, dropping the check for the actually used protocol (with respHttpVersion). In practice, most H3 deployments will emit alt-svc headers on H3 responses as well, so these should overlap anyway. This could however diverge in the future if people deploy significantly different setups for H3 compared to H2, but at least for now I'd be surprised to find a large discrepancy. For future proofness, it's of course best to keep respHttpVersion as well.

• I'd really like to find out if chrome is abandoning existing H2 connections when H3 has been established, or if it's just using H3 for new connections (e.g., like you say, differently credentialed). I'm not sure how easy it is to check that (or if you want to include that in this query or another for the Almanac say), but I was hoping maybe there's like a isCredentialed field somewhere that might give an indication? Knowing this might have a big impact on how you explain the results + also on how people should interpret their own results going forward.

[tunetheweb]

h3 is already "officially" in use today. Even though the RFC hasn't landed, the IETF decided to just start deploying h3 together with QUIC v1 (RFC9000 and siblings). Most big deployments today do both h3 and h3-29 IIUC, the latter primarily to support older clients (e.g., mainline version of Safari only does h3-29 for now). It's a small nit, but somewhat important :)

I'm not sure that's quite true yet. The June crawl is just finishing but for the May crawl I saw very little h3 advertisement sin alt-svc. And my own Chrome is still using h3-29 for example even when h3 is supported by the server (though is alt-svc is preferred order, cause h3-27 is listed before h3?).

But anyway, I agree it's a short term measure and h3-29 is, to all intents and purposes, h3 so happy to include both.

If query cost is the problem, then I don't think it'd be such a big problem to cut down the logic to just checking alt-svc, dropping the check for the actually used protocol (with respHttpVersion).

Actually checking the alt-svc header is more expensive that the req/resp version 😁 But anyway it's not an issue. Just didn't want to parse out the _protocol from the HAR across every request for ever month, which is what the HTTP/2 query is currently doing cause that is REALLY expensive.

I'd really like to find out if chrome is abandoning existing H2 connections when H3 has been established, or if it's just using H3 for new connections (e.g., like you say, differently credentialed)

Let's take this point off line as not really related to this PR. We can explore as part of the HTTP chapter of the Web Almanac. I would ask have you any evidence to suggest it will abandon connections to switch to HTTP/3 connections? Seems inefficient when a connection is already established.

[tunetheweb]

Just follow up, I did some more digging on the "dip":

 select '2020_05_01' as date, count(1) as NumResponses,
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') LIKE '%h3%') as anyh3,
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') LIKE '%h3-27=%') as h327,
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') LIKE '%h3-29=%') as h329,
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') = 'clear') as clear,
 COUNTIF(respOtherHeaders LIKE '%alt-svc%') as altsvc,
 COUNTIF(lower(_cdn_provider) LIKE '%cloudflare%') as cloudflare,
 COUNTIF(lower(_cdn_provider) LIKE '%cloudflare%' AND respOtherHeaders LIKE '%alt-svc%') as cloudflare_altsvc,
 COUNTIF(lower(_cdn_provider) LIKE '%google%') as google,
 COUNTIF(lower(_cdn_provider) LIKE '%google%' AND respOtherHeaders LIKE '%alt-svc%') as google_altsvc
 from `httparchive.summary_requests.2020_05_01_desktop`
 UNION ALL
 select '2020_06_01' as date, count(1) as NumResponses,
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') LIKE '%h3%') as anyh3,
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') LIKE '%h3-27=%') as h327,
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') LIKE '%h3-29=%') as h329,
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') = 'clear') as clear,
 COUNTIF(respOtherHeaders LIKE '%alt-svc%') as altsvc,
 COUNTIF(lower(_cdn_provider) LIKE '%cloudflare%') as cloudflare,
 COUNTIF(lower(_cdn_provider) LIKE '%cloudflare%' AND respOtherHeaders LIKE '%alt-svc%') as cloudflare_altsvc,
 COUNTIF(lower(_cdn_provider) LIKE '%google%') as google,
 COUNTIF(lower(_cdn_provider) LIKE '%google%' AND respOtherHeaders LIKE '%alt-svc%') as google_altsvc
 from `httparchive.summary_requests.2020_06_01_desktop`
 UNION ALL
 select '2020_07_01' as date, count(1) as NumResponses,
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') LIKE '%h3%') as anyh3,
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') LIKE '%h3-27=%') as h327,
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') LIKE '%h3-29=%') as h329,
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') = 'clear') as clear,
 COUNTIF(respOtherHeaders LIKE '%alt-svc%') as altsvc,
 COUNTIF(lower(_cdn_provider) LIKE '%cloudflare%') as cloudflare,
 COUNTIF(lower(_cdn_provider) LIKE '%cloudflare%' AND respOtherHeaders LIKE '%alt-svc%') as cloudflare_altsvc,
 COUNTIF(lower(_cdn_provider) LIKE '%google%') as google,
 COUNTIF(lower(_cdn_provider) LIKE '%google%' AND respOtherHeaders LIKE '%alt-svc%') as google_altsvc
 from `httparchive.summary_requests.2020_07_01_desktop`
 UNION ALL
 select '2020_08_01', count(1),
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') LIKE '%h3%') as anyh3,
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') LIKE '%h3-27=%') as h327,
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') LIKE '%h3-29=%') as h329,
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') = 'clear') as clear,
 COUNTIF(respOtherHeaders LIKE '%alt-svc%') as altsvc,
 COUNTIF(lower(_cdn_provider) LIKE '%cloudflare%') as cloudflare,
 COUNTIF(lower(_cdn_provider) LIKE '%cloudflare%' AND respOtherHeaders LIKE '%alt-svc%') as cloudflare_altsvc,
 COUNTIF(lower(_cdn_provider) LIKE '%google%') as google,
 COUNTIF(lower(_cdn_provider) LIKE '%google%' AND respOtherHeaders LIKE '%alt-svc%') as google_altsvc
 from `httparchive.summary_requests.2020_08_01_desktop`
 UNION ALL
 select '2020_09_01', count(1),
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') LIKE '%h3%') as anyh3,
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') LIKE '%h3-27=%') as h327,
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') LIKE '%h3-29=%') as h329,
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') = 'clear') as clear,
 COUNTIF(respOtherHeaders LIKE '%alt-svc%') as altsvc,
 COUNTIF(lower(_cdn_provider) LIKE '%cloudflare%') as cloudflare,
 COUNTIF(lower(_cdn_provider) LIKE '%cloudflare%' AND respOtherHeaders LIKE '%alt-svc%') as cloudflare_altsvc,
 COUNTIF(lower(_cdn_provider) LIKE '%google%') as google,
 COUNTIF(lower(_cdn_provider) LIKE '%google%' AND respOtherHeaders LIKE '%alt-svc%') as google_altsvc
 from `httparchive.summary_requests.2020_09_01_desktop`
 UNION ALL
 select '2020_10_01', count(1),
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') LIKE '%h3%') as anyh3,
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') LIKE '%h3-27=%') as h327,
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') LIKE '%h3-29=%') as h329,
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') = 'clear') as clear,
 COUNTIF(respOtherHeaders LIKE '%alt-svc%') as altsvc,
 COUNTIF(lower(_cdn_provider) LIKE '%cloudflare%') as cloudflare,
 COUNTIF(lower(_cdn_provider) LIKE '%cloudflare%' AND respOtherHeaders LIKE '%alt-svc%') as cloudflare_altsvc,
 COUNTIF(lower(_cdn_provider) LIKE '%google%') as google,
 COUNTIF(lower(_cdn_provider) LIKE '%google%' AND respOtherHeaders LIKE '%alt-svc%') as google_altsvc
 from `httparchive.summary_requests.2020_10_01_desktop`
 UNION ALL
 select '2020_11_01', count(1),
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') LIKE '%h3%') as anyh3,
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') LIKE '%h3-27=%') as h327,
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') LIKE '%h3-29=%') as h329,
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') = 'clear') as clear,
 COUNTIF(respOtherHeaders LIKE '%alt-svc%') as altsvc,
 COUNTIF(lower(_cdn_provider) LIKE '%cloudflare%') as cloudflare,
 COUNTIF(lower(_cdn_provider) LIKE '%cloudflare%' AND respOtherHeaders LIKE '%alt-svc%') as cloudflare_altsvc,
 COUNTIF(lower(_cdn_provider) LIKE '%google%') as google,
 COUNTIF(lower(_cdn_provider) LIKE '%google%' AND respOtherHeaders LIKE '%alt-svc%') as google_altsvc
 from `httparchive.summary_requests.2020_11_01_desktop`
 UNION ALL
 select '2020_12_01', count(1),
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') LIKE '%h3%') as anyh3,
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') LIKE '%h3-27=%') as h327,
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') LIKE '%h3-29=%') as h329,
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') = 'clear') as clear,
 COUNTIF(respOtherHeaders LIKE '%alt-svc%') as altsvc,
 COUNTIF(lower(_cdn_provider) LIKE '%cloudflare%') as cloudflare,
 COUNTIF(lower(_cdn_provider) LIKE '%cloudflare%' AND respOtherHeaders LIKE '%alt-svc%') as cloudflare_altsvc,
 COUNTIF(lower(_cdn_provider) LIKE '%google%') as google,
 COUNTIF(lower(_cdn_provider) LIKE '%google%' AND respOtherHeaders LIKE '%alt-svc%') as google_altsvc
 from `httparchive.summary_requests.2020_12_01_desktop`
 UNION ALL
 select '2021_01_01', count(1),
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') LIKE '%h3%') as anyh3,
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') LIKE '%h3-27=%') as h327,
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') LIKE '%h3-29=%') as h329,
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') = 'clear') as clear,
 COUNTIF(respOtherHeaders LIKE '%alt-svc%') as altsvc,
 COUNTIF(lower(_cdn_provider) LIKE '%cloudflare%') as cloudflare,
 COUNTIF(lower(_cdn_provider) LIKE '%cloudflare%' AND respOtherHeaders LIKE '%alt-svc%') as cloudflare_altsvc,
 COUNTIF(lower(_cdn_provider) LIKE '%google%') as google,
 COUNTIF(lower(_cdn_provider) LIKE '%google%' AND respOtherHeaders LIKE '%alt-svc%') as google_altsvc
 from `httparchive.summary_requests.2021_01_01_desktop`
 UNION ALL
 select '2021_02_01', count(1),
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') LIKE '%h3%') as anyh3,
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') LIKE '%h3-27=%') as h327,
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') LIKE '%h3-29=%') as h329,
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') = 'clear') as clear,
 COUNTIF(respOtherHeaders LIKE '%alt-svc%') as altsvc,
 COUNTIF(lower(_cdn_provider) LIKE '%cloudflare%') as cloudflare,
 COUNTIF(lower(_cdn_provider) LIKE '%cloudflare%' AND respOtherHeaders LIKE '%alt-svc%') as cloudflare_altsvc,
 COUNTIF(lower(_cdn_provider) LIKE '%google%') as google,
 COUNTIF(lower(_cdn_provider) LIKE '%google%' AND respOtherHeaders LIKE '%alt-svc%') as google_altsvc
 from `httparchive.summary_requests.2021_02_01_desktop`
 UNION ALL
 select '2021_03_01', count(1),
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') LIKE '%h3%') as anyh3,
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') LIKE '%h3-27=%') as h327,
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') LIKE '%h3-29=%') as h329,
 COUNTIF(REGEXP_EXTRACT(REGEXP_EXTRACT(respOtherHeaders, r'alt-svc = (.*)'), r'(.*?)(?:, [^ ]* = .*)?$') = 'clear') as clear,
 COUNTIF(respOtherHeaders LIKE '%alt-svc%') as altsvc,
 COUNTIF(lower(_cdn_provider) LIKE '%cloudflare%') as cloudflare,
 COUNTIF(lower(_cdn_provider) LIKE '%cloudflare%' AND respOtherHeaders LIKE '%alt-svc%') as cloudflare_altsvc,
 COUNTIF(lower(_cdn_provider) LIKE '%google%') as google,
 COUNTIF(lower(_cdn_provider) LIKE '%google%' AND respOtherHeaders LIKE '%alt-svc%') as google_altsvc
 from `httparchive.summary_requests.2021_03_01_desktop`
 order by date

date	NumResponses	anyh3	h327	h329	clear	altsvc	cloudflare	cloudflare_altsvc	google	google_altsvc
2020_05_01	428,682,018	27,746,788	22,798,551	-	5,277,549	36,198,824	28,713,543	4,150,889	57,374,782	13,656,478
2020_06_01	469,139,890	36,763,496	35,881,965	560,212	5,842,791	46,016,229	31,631,376	4,955,435	65,408,210	16,208,973
2020_07_01	522,565,781	39,928,766	39,004,480	37,384,205	6,785,097	50,364,263	34,504,992	5,575,735	72,588,021	17,548,632
2020_08_01	528,007,479	34,514,143	33,527,276	32,970,726	7,233,250	45,307,828	35,294,546	5,807,460	73,124,647	13,883,805
2020_09_01	509,287,871	30,193,289	29,209,105	28,626,473	6,868,581	40,213,872	35,059,563	5,939,923	74,257,012	11,154,994
2020_10_01	507,355,897	29,329,196	28,222,077	27,717,555	6,633,540	38,960,091	36,662,363	6,460,057	74,981,572	9,649,130
2020_11_01	532,631,230	17,980,993	8,888,169	16,455,247	7,029,486	28,050,663	38,181,154	9,441	78,489,040	11,079,412
2020_12_01	557,193,476	20,904,437	14,182,531	18,083,565	7,150,731	31,013,781	40,301,075	22,467	82,325,602	9,000,699
2021_01_01	565,109,617	17,413,671	14,406,923	14,399,602	7,238,880	27,390,956	41,674,815	9,255	83,585,408	6,172,171
2021_02_01	523,659,691	27,226,928	23,636,765	23,409,535	7,021,916	35,690,621	40,578,882	8,244,980	74,683,536	5,777,712
2021_03_01	579,860,833	34,534,890	30,846,356	30,654,687	7,823,140	42,964,473	45,211,572	14,010,892	80,145,972	5,372,676

The drop from August 2020 looks to be with Google disabling alt-svc.

And similarly, apparently Cloudflare disabled QUIC for a bit while investigating issues - which is what we see in Nov 2020 - Jan 2021.

Either way our metrics are also reflected in other graphs from other providers, so do think our graph is accurately reflecting support.