YouTube Thumbnail Not Showing, Not Updating or Blurry: Check These in Order

Timeline: one thumbnail change, measured

The hq720 copy changed in batches. The same hq720 address returned the new image at 12 s, the old one at 51 s, the new one at 1 min 31 s, the old one again at 2 min 9 s, and the new one at every check from 4 min 9 s on. That is five changes counting the first. Refreshing during that window can show the new thumbnail and then the old one.

Two address forms did not follow the change. By our first check, 12 seconds after saving, the channel page no longer listed the oardefault address for the Short's vertical thumbnail. It listed the same set of addresses as later checks whose image we fetched from a new sardefault address. The old oardefault and oar2 addresses kept serving the old image for as long as we watched. A website, app or chat preview that saved one of those addresses keeps showing the old thumbnail.

What this test does and does not show. It is one Short, one channel, one computer on one network, and one change. Checks ran roughly every 40 to 80 seconds for the first 45 minutes, apart from one 2-minute gap between 2 min 9 s and 4 min 9 s, and about every 2 min 15 s after that. Each time is the first check that showed a change, so the change itself happened somewhere in the gap before it. Our script did not request the sardefault address until 13 min 15 s; one manual request at 12 min 31 s is timed by the saved file. We did not test the YouTube phone app, other countries, or a regular video, so these times are this test's timetable, not a rule. In an earlier test on October 6, channel cards still showed the old image 95 seconds after saving.

Download the timed log (every check, file checksum and cache header)

Find your symptom

Most thumbnail problems fall into one of three groups. If you can't add a custom thumbnail, check that your account is verified and your file fits the upload limits. If you saved a new thumbnail but still see the old one, wait a few minutes, then reload, and check whether you are looking at an old image address (see the timeline above). If the thumbnail looks blurry, upload at least 1280 × 720 and check which copy you are looking at, because YouTube serves the same thumbnail in five sizes. Add custom thumbnails and Create YouTube Shorts · checked October 10, 2026

Cache headers on 75 thumbnail files (measured)

YouTube Help says "It may take time for your thumbnail changes to appear on YouTube" but gives no figure. So we looked at what the image server itself tells browsers.

On October 9, 2026 we requested all five public thumbnail sizes for each of the 15 videos on our channel (14 regular videos and 1 Short), 75 image files in total.

Every regular video's thumbnail was sent with Cache-Control: public, max-age=7200. That allows a browser, or any cache between it and YouTube, to reuse its saved copy for 2 hours without asking again. The Short's files were sent with max-age=300, or 5 minutes.

What this means in practice:

1. Right after you save, your own browser may show the old copy for up to 2 hours. A hard reload (Ctrl + Shift + R, or Cmd + Shift + R on a Mac) asks for a fresh copy.
2. Other viewers, websites that embed your video, and link previews in apps keep their own copies on their own schedules. We did not measure those.
3. The cache instruction is a ceiling for one copy, not a promise about when YouTube finishes processing. It does not explain a thumbnail that is still old days later.

Download the 75 measurements (status, pixel size, bytes, SHA-256 and cache header for each file)

Why a thumbnail looks blurry

A sharp thumbnail needs a large upload, and it needs the viewer to be served a large copy.

Your upload. YouTube recommends 3840 × 2160 for videos and 2160 × 3840 for Shorts, with a minimum width of 640 pixels for videos; our size guide lists the full official specs. Under the 2 MB mobile limit, a large JPG may need a lower quality setting, which adds blocky artefacts; uploading from a computer allows 50 MB. Our compression study shows what each quality step does to fine text.

The copy being shown. The five copies above differ a lot. The picture inside hqdefault is only 480 × 270, because the file is 4:3 with black bars above and below. That is 9/64, about 14%, of the pixels in the 1280 × 720 copy. A site or app that uses hqdefault and stretches it larger will look soft however good your upload is. Our resolution measurements show the bars row by row.

from fractions import Fraction as F
picture = F(480 * 270, 1280 * 720)          # hqdefault picture area vs maxresdefault
assert picture == F(9, 64) and round(float(picture) * 100) == 14
assert 7200 // 3600 == 2 and 300 // 60 == 5  # max-age values in hours and minutes
assert 15 * 5 == 75                          # videos x copies requested
assert (5 * 60 + 31) - (1 * 60 + 22) == 249  # hq720: first check that stayed new, 06:05:31, minus save at 06:01:22, seconds
assert (13 * 60 + 53) - (1 * 60 + 22) == 12 * 60 + 31  # manual sardefault request, saved 06:13:53
print('Troubleshooting checks passed')

Pixelated text. Small text breaks up first. Check your design at the size viewers really see it in our thumbnail tester before uploading.

When nothing loads at all

If thumbnails are missing on every channel, not just yours, the cause is on the viewing side. Common suggestions in the top search results include trying another browser, turning off extensions and content blockers, and clearing the browser cache. These are general steps; we have not tested them here.

To see which copies of a public video's thumbnail YouTube is serving right now, paste its link into the thumbnail downloader. It lists every size that loads.

Before you contact YouTube

• Your account is verified and the Upload file button is there.
• The file is a JPG or PNG under 2 MB (mobile) or 50 MB (computer).
• Videos use 16:9; Shorts and other vertical videos use 9:16.
• You waited at least 2 hours and did a hard reload.
• The thumbnail follows the Community Guidelines.