About

GIF animation length depends on two factors: the number of frames (N) and the per-frame delay (d), measured in hundredths of a second. Total duration equals N × d. Modifying either variable changes perceived length. This tool parses the raw GIF89a binary, extracts every Graphic Control Extension block, and lets you trim frame ranges or uniformly scale delay values. No server upload occurs. Processing runs entirely in your browser via a Web Worker performing LZW decompression and recompression.

Incorrect delay manipulation can produce GIFs that stutter or exceed platform file-size limits. Some frames carry local color tables or use disposal methods that, if stripped, cause visual artifacts. This tool preserves disposal flags and local palettes during re-encoding. Note: the GIF specification caps per-frame delay at 655.35 s. Extremely large files (>20 MB) or GIFs exceeding 1000 frames may cause memory pressure in constrained environments.

Formulas

The total duration of a GIF animation is computed from the sum of all individual frame delays:

T = N∑i=1 d_i

Where T = total duration in hundredths of a second, N = total number of frames, d_i = delay of the i-th frame in hundredths of a second (stored as a 16-bit unsigned little-endian integer in the Graphic Control Extension block).

When changing speed by a factor s, each frame delay is scaled:

d_i^′ = round(d_is)

Where s > 1 speeds up (shorter delays), s < 1 slows down (longer delays). The minimum clamped delay is 2 (= 20 ms) because most browsers treat 0 or 1 as ~100 ms. Maximum is 65535 (655.35 s).

When trimming, the output contains frames from index a to b (inclusive), producing b − a + 1 frames. The new duration becomes:

T^′ = b∑i=a d_i^′

Reference Data

Platform	Max GIF Size	Max Duration	Max Dimensions	Recommended FPS	Notes
Twitter/X	15 MB	140 s	1280×1080 px	10 - 15	Auto-converts to MP4
Discord	8 MB (free) / 50 MB (Nitro)	No limit	No limit	15 - 25	Avatar GIFs: 10 MB
Slack	20 MB	No limit	No limit	10 - 20	Large GIFs preview poorly
Reddit	20 MB	60 s	1280×720 px	10 - 15	Converted to MP4 on upload
Tumblr	10 MB	No limit	540 px wide	10 - 15	Resized if wider
GIPHY	100 MB	15 s recommended	720 px wide	15 - 24	Optimized on ingest
Facebook	8 MB	No limit	No limit	10 - 15	Only via GIPHY integration
iMessage	5 MB	No limit	No limit	10 - 15	Larger GIFs sent as files
WhatsApp	16 MB	No limit	No limit	10 - 15	Auto-compressed
LinkedIn	5 MB	No limit	No limit	10	GIFs in comments only
Email (General)	1 - 3 MB	<6 s	600 px wide	8 - 12	Some clients block animation
GIF87a Spec	No limit	No limit	65535×65535 px	N/A	No animation support
GIF89a Spec	No limit	Max delay: 655.35 s/frame	65535×65535 px	Up to 100	Supports transparency & animation
Photoshop Export	No limit	No limit	30000×30000 px	15 - 30	Save for Web (Legacy)

Frequently Asked Questions

The GIF specification allows frame delays as low as 0 (= 0 ms), but most browsers clamp delays below 2 (= 20 ms) to approximately 100 ms. This tool enforces a minimum delay of 20 ms per frame to ensure consistent playback across Chrome, Firefox, and Safari.

Disposal method 3 ('restore to previous') tells the renderer to revert to the canvas state before the current frame was drawn. If you trim the beginning of a GIF, the first trimmed frame might reference a state that no longer exists. This tool automatically changes the first frame's disposal method to 1 ('do not dispose') to prevent rendering artifacts.

GIF compression relies on LZW encoding, which is dictionary-based. When frames are re-encoded independently, the new LZW stream may not achieve the same compression ratio as the original, especially if the original used cross-frame optimizations (delta encoding). For minimal size increase, avoid re-encoding when only adjusting speed - this tool modifies delay bytes in-place for speed-only changes.

Each frame can have a local color table of up to 256 colors (8-bit indexed). The global color table also holds up to 256 entries. Different frames can use different local tables, so the total unique colors across the entire animation can exceed 256, but never within a single frame.

Yes. The timeline displays each frame with its individual delay value. You can click any frame, modify its delay, and the change applies only to that frame. This is useful for creating pause effects (high delay on one frame) or acceleration sequences.

Negligibly. The loop count is stored in the Netscape Application Extension block as a single 16-bit value. Changing it from infinite (0) to a fixed count alters only 2 bytes in the output.

This tool preserves the transparent color index from each frame's Graphic Control Extension. If a frame declares index 7 as transparent, that mapping is maintained in the re-encoded output. No transparency data is lost during processing.