View previews
Preview mode displays the opposite pane’s current file. It lets you view local or S3 files without modifying them. For S3, it reads or downloads data from the service: check the limits below before browsing large files.
Display a preview
For an Amazon S3 object, you need s3:GetObject, or s3:GetObjectVersion to read a specific version. Permission to list objects is not enough to read their content. For an SSE-KMS object, you also need kms:Decrypt and kms:GenerateDataKey permissions for the key. See AWS GetObject documentation.
- Keep one pane in Tree and list view, Tree view, or List view.
- In View > Left view or View > Right view, choose Preview for the opposite side. You can also use its view selector.
- Select the file in the browsing pane.
- Wait for it to load, then use the controls for its content type.
- To browse on both sides again, choose a browsing view in the preview pane.
Selecting a folder prompts you to choose a file. With multiple selection, the preview follows the current file rather than all selected files. If both panes use Preview, neither supplies a file to the other and both previews are empty.
Formats and viewing controls
S3Client chooses the preview type from the filename extension. Image support depends on the formats available in Qt; .pdf files use the PDF reader. Text and audio or video types also use the associations in Tools > Content types…. An association does not guarantee that a codec can decode the file. See content types.
The Content-Type returned by S3 does not select the preview reader. For text, its charset can determine decoding. PDF extensions, supported image extensions, and recognized media extensions retain their specialized readers even when associated with a text type. Other extensions associated with audio/* or video/* use the media player.
| Type | Controls and information |
|---|---|
| Still image | Zoom in, Zoom out, Rotate left, and Rotate right change the display. The mouse wheel zooms around the pointer; drag the image to pan when zoomed in. Initially, large images fit the pane and small images retain their size. The status bar shows the format, dimensions, decoded depth, alpha channel, and zoom; color space and resolution appear when known. |
| Animated image | Play and Pause control the animation. |
| Previous page, Next page, and Page change pages. Fit page fits the page into the display area; Zoom in and Zoom out adjust magnification. | |
| Text | Text is read-only, without automatic line wrapping. You can select and copy it. The status bar shows the encoding, amount loaded, and Complete preview or Partial preview. |
| Audio or video | Play, Pause, Return to beginning, Playback position, Volume, and Mute control playback. You can choose a playback position if the media supports it and its duration is known. Returning to the beginning becomes available once playback has started. Volume and Mute are available when the media contains audio. Retry preview, when available after a media error, prepares the media again. |
A password-protected PDF displays Password:. Enter the document password and click Open; it is separate from account credentials and any SSE-C key. Zooming and rotation do not modify the source file.
When the preview pane has focus, Space toggles Play and Pause for an animation or media file. Volume and Mute settings carry over to subsequent media previews. S3 streaming in the status bar identifies an S3 range stream; Buffering… means the player is waiting for data.
To copy a decoded still image, use Copy image to clipboard in the file’s context menu in the browsing pane. This command may read or download the image if it is not already available and obeys the image size limit.
You can also right-click the image in the preview and choose Copy image to clipboard. For an animation, this copies the current frame. The copy retains the decoded pixels without applying display zoom or rotation.
Playlists or manifests such as .m3u, .m3u8, .pls, .mpd, and .xspf do not start the media they reference. They are treated as text if their association permits it; otherwise, no preview is available.
Downloads and size limits
Image previews require the entire file content, which must be strictly smaller than the configured threshold. For a gzip S3 response, the threshold applies to file content after decompression, before image decoding. Reading or downloading may have started before the preview is refused. S3 PDFs are downloaded in full before viewing; local PDFs use the local file directly or an in-memory copy. Text previews load only the beginning, up to the configured limit. S3 media is read in byte ranges and can start before the entire file has been downloaded.
To change settings, open Tools > Options…, select Preview, and click OK. Cancel discards changes. Then select another file and return to the original one to rebuild its preview with the new settings.
| Group and option | Values and effect |
|---|---|
| Images > Do not preview images of at least: | 1 to 1,024 MiB; default 10 MiB. Sizes at or above the threshold are refused: local file size, S3 content without HTTP compression, or content after gzip decompression. An S3 request and partial transfer may occur before refusal. Decoded pixels may require more memory than this size. |
| PDF > Limit PDF downloads to: | On by default at 256 MiB; 1 to 2,147,483,647 MiB. S3 PDFs above this limit are refused; a file exactly at the limit is accepted. For gzip, the limit bounds both downloaded bytes and decompressed content. Clear the checkbox to remove the download limit. It does not apply to local PDFs or bound all memory used by the PDF reader. |
| Preview downloads > Maximum concurrent requests per preview: | 1 to 32; default 4. Caps simultaneous requests for one S3 image, PDF, or media preview. A value of 1 disables parallel downloading. Global execution limits also apply. |
| Preview downloads > Parallel download threshold: | 64 to 1,048,576 KiB; default 256 KiB. For objects at or above this size, S3 image, PDF, and media previews may request several ranges concurrently. Text does not use parallel downloading. |
| Text > Maximum text preview content: | 1 to 64 KiB; default 64 KiB. Limits bytes read or downloaded as well as decompressed content. Larger text files produce partial previews. |
| Text > Text preview font: | Selects an installed font. With no saved preference, S3Client uses a system fixed-width font. |
| Text > Text preview font size: | 6 to 96 points, with one decimal place. With no saved preference, the size comes from the default font. |
| Multimedia > Play automatically | Off by default. Starts media playback after preparation and animated images after loading; otherwise, click Play. |
| Multimedia > Media cache size: | 1 to 1,048,576 MiB; default 16 MiB. Limits cached data per S3 media preview. A media file can be larger than this cache. The total memory used for playback can exceed this limit. |
MiB and KiB are binary units: 1 MiB is 1,048,576 bytes and 1 KiB is 1,024 bytes. Image, PDF, and text limits are independent.
Parallel downloading is possible only if S3Client can verify that the parts being read belong to the same file version and the service accepts byte-range reads. The configured request count is a maximum; some files use fewer requests.
Cache and partial previews
The media cache keeps already loaded parts of the current media file in memory. Choosing another playback position, or returning to a part that is no longer cached, may trigger more S3 reads. Changing files or leaving preview cancels reads that are no longer needed and releases this cache. It does not provide a permanent copy for offline viewing.
An S3 PDF may be held in memory or in a temporary file, depending on its size and available memory. The file contains the received data after any decompression; S3Client does not encrypt it locally, even if the object uses server-side encryption. Any password protection within the PDF remains separate. S3Client removes the temporary file when it releases that preview. Allow space in the system temporary directory for large PDFs.
Partial preview means only the start of the text was read, or the decompression limit was reached. It cannot verify the end of the file or the full integrity of a truncated gzip stream. To view the entire content, download the file and open it in a suitable application; increasing the text limit cannot exceed 64 KiB.
Text decoding first uses the byte order mark (BOM), then the charset in the received or extension-associated content type, then UTF-8. Decoding errors or encoding mismatch reports invalid characters, an unknown declared encoding, or an encoding conflict. Check the file and its metadata or type association before relying on the displayed text.
Encryption, archives, and read errors
Older object versions can be previewed when their content is accessible. Delete markers display Delete markers cannot be previewed. and cannot be read.
An archived object must be restored and readable before previewing it. A visible list entry does not prove that its data is immediately available. Use Restore archived object… in the browsing pane when offered, then wait for restoration to finish. See storage classes and archives.
The source object is archived and must be restored before its content can be read. requires restoration. The source object is being restored and is not readable yet. means you must wait for it to finish. The source storage class is not configured for this bucket. means the account policy does not describe that class for the bucket: check File > Accounts… > Edit… > Capabilities > Storage classes and the applicable policy before retrying the preview.
SSE-C reads require HTTPS and are not offered for directory buckets. In File > Accounts…, select the account, click Edit…, and open Capabilities > Encryption. Check SSE-C if the service supports it. Then open Encryption policies > Features. Under Policy, choose the encryption policy applying to the bucket, then check SSE-C operations > SSE-C reading > Read object data and Read object metadata as needed by the reads performed. Check Account default policy and bucket assignments under Assignments, then save the account with OK. These settings supply neither keys nor permissions. See account capabilities.
If an S3 read fails before obtaining content and the account supports that SSE-C read, SSE-C read key… may become available in the preview. It also remains available while a temporary key is in use.
- Click SSE-C read key….
- In SSE-C read key, choose Temporary SSE-C key.
- Under Encoding:, choose Base64 or Hexadecimal, then enter Key:. The decoded key must contain exactly 32 bytes; hexadecimal input requires 64 characters.
- Alternatively, click Import file… and choose a binary file containing exactly 32 bytes.
- Click OK to retry the preview with this key.
No SSE-C key retries without a supplied key. The temporary key is not saved as an account setting; changing objects resets this choice. Supplying a key cannot fix a format error after a successful read.
S3 images, PDFs, and text can be decompressed when the response declares Content-Encoding: gzip, within their respective limits. S3 media range streaming refuses HTTP compression: Streaming cannot read an object stored with HTTP content compression. identifies this restriction. Download the content to view it another way.
This file cannot be previewed. identifies an unsupported type. The media format or codec cannot be decoded. means the media player cannot decode the content. Unable to load the preview. is followed by the read failure’s cause; check the connection, permissions, key, and object availability. After resolving it, change the selection and return to the file, or use Retry preview for media when available.
Incorrect password. Please try again. asks for another PDF password. This PDF uses an unsupported security scheme. means the PDF reader does not support the document’s protection: download it and open it in a compatible reader. These errors concern the document already loaded, rather than S3 permissions.