The latest stats show continued HTTP/2 adoption. Was 40% last we checked in June 2018.
#standardSQL
# WARNING: 4.04 TB query!
SELECT
_TABLE_SUFFIX AS client,
ROUND(SUM(IF(JSON_EXTRACT_SCALAR(payload, '$._protocol') = 'HTTP/2', 1, 0)) * 100 / COUNT(0), 2) AS percent
FROM
`httparchive.requests.2019_02_01_*`
GROUP BY
client
| client | percent |
|---|---|
| mobile | 49.84 |
| desktop | 49.72 |