iOS: Chinese subtitles show boxes on iPhone 17 Pro Max

Plex Players
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Hi Plex team/community,

I’m seeing an iOS subtitle rendering issue where Chinese characters display as square “box” glyphs (□□□) instead of Chinese characters. This is still happening on my iPhone 17 Pro Max even after updating to the latest Plex iOS app and the latest iOS update.

My subtitles are bilingual (English + Chinese), and the English displays correctly—it’s only the Chinese portion that turns into boxes/squares. I tested both Traditional and Simplified Chinese, and both have the same issue.

Also, to rule out bad subtitle sources: I create/edit my subtitles myself using Subtitle Edit, and I’ve tested multiple subtitle formats. I have tried SRT (.srt), SMI (.smi), SSA/ASS (.ssa/.ass), and WebVTT (.vtt)—and the issue still happens (Chinese still renders as boxes on iOS).

I also tested different containers: it’s not limited to MKV. Even MP4 files show the same problem—Chinese characters still render as boxes on iOS.

On top of that, if I enable Forced subtitles, playback often does not play properly (stutters/freezes, audio/video goes out of sync, or the video keeps buffering / won’t continue smoothly). Turning Forced subtitles off usually makes playback normal again.

I’ve attached an iPhone Plex screenshot showing the boxed subtitles. I wanted to attach the .ASS subtitle file too, but I can’t upload .ASS files on the forum, so I’m attaching the .SRT file version for the same movie instead.

Setup

  • Device: iPhone 17 Pro Max (iOS: 26.2.1)

  • Plex for iOS version: 2026.1.0 (latest as of today)

  • Plex Media Server: 1.43.0.10492 running on Synology DS923+/DSM 7.3.2-86009

  • Media location: Movies stored on my Synology NAS

  • Containers tested: MKV and MP4

  • Subtitles: Bilingual (English + Chinese) (English OK; Chinese renders as boxes)

  • iOS app setting: Subtitles set to Automatic

Repro (Chinese renders as boxes)

  1. Open Plex on iPhone and play a movie with bilingual subtitles (tested MKV + MP4)

  2. Let “Automatic” choose the subtitle track (or manually select the bilingual track)

  3. English renders fine, but Chinese characters render as boxes/squares (Traditional + Simplified both tested)

Repro (Forced subtitles playback issue)

  1. Start the same movie

  2. Enable Forced subtitles (or select the subtitle track that is marked Forced)

  3. Playback becomes unstable (stutter/freeze/out-of-sync/buffering) and may not play smoothly

Expected

  • Chinese characters render correctly (English already does)

  • Playback remains smooth even with Forced subtitles enabled

Actual

  • Chinese characters render as boxes/squares (unreadable), while English is OK

  • Forced subtitles can make playback unreliable

Troubleshooting tried

  • Confirmed Subtitles = Automatic (and also tried manually selecting tracks)

  • Restarted device, reinstalled Plex app

  • Tested multiple movies/subtitle tracks (same result)

Questions:

  1. Is this a known iOS regression or a font/subtitle-renderer issue (CJK glyph support)?

  2. Any recommended workaround (subtitle encoding/font settings, burn-in behavior, or forcing a different subtitle renderer)?

  3. What exact logs/details would you like me to attach?

Thanks in advance,
Felix

Doom.2005.BDREMUX.2160p.HDR.seleZen.srt (142.7 KB)

IMG_0872.PNG
IMG_0872.PNG1920×884 251 KB

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