Reddit Ad Specs: Dimensions, File Sizes, and Character Limits Cheat Sheet

Nothing kills momentum like uploading a creative and having it rejected on a spec technicality. This is a working reference for Reddit ad specs across the main formats, plus the practical rules that keep your assets clean and approvable. Use it as a pre-flight checklist before every upload.

One important note up front: Reddit updates its exact specs periodically, and the authoritative source is always the field-level guidance inside Reddit Ads Manager at the moment you upload. Treat the numbers below as the reliable working ranges to design around, and confirm any hard limit against the platform before a big launch.

Image Ad Specs

The single-image Promoted Post is the workhorse format, so get these right.

• Recommended aspect ratio: 1:1 (square) is the safest, most flexible choice across placements. 4:5 (portrait) also performs well in-feed.
• Recommended resolution: aim high, at least 1200 x 1200 px for a square, so the asset stays crisp on high-density screens and across placements.
• File types: PNG and JPG are the standard accepted types. GIF support varies by placement.
• File size: keep images comfortably under the platform limit (design to a few MB rather than pushing the ceiling) to avoid upload issues.
• Design safety: keep essential text and logos away from the extreme edges so nothing important is clipped when the asset is cropped for different placements.

Video Ad Specs

• Aspect ratios: 1:1 (square) and 4:5 (portrait) are the strongest in-feed. 16:9 works for landscape contexts. Design the important action to survive a square crop.
• Resolution: 1080p is the sensible target. Higher is fine; lower looks cheap.
• File types: MP4 and MOV are the standard accepted containers.
• Length: shorter wins. Front-load the hook in the first two seconds. Most Reddit video is watched muted, so plan for a silent first impression.
• Captions: burn captions into the file rather than relying on optional caption tracks. If the message does not land without sound, it does not land.
• File size: stay well under the platform ceiling to keep uploads smooth.

Carousel Ad Specs

• Cards: a carousel holds multiple cards (typically between two and six). Every card should earn its swipe.
• Per-card image: follow the single-image specs above, favouring a consistent aspect ratio (1:1) across all cards for a clean swipe.
• Per-card copy: each card can carry its own headline and destination URL. Keep headlines tight and consistent in tone.

Text / Free-Form Ad Specs

• No image required. The format is headline plus body text.
• Headline: short and punchy beats long. A strong headline is the entire ad here, so treat it accordingly.
• Body copy: you have room for more than a headline, but Reddit rewards brevity and a conversational voice. Say the interesting thing and stop.

Copy and Character Limits

Exact character counts vary by placement and change over time, so the reliable rule is to design short and let Reddit Ads Manager show you the live limit as you type.

• Headlines: write to roughly 40 to 60 characters for full display without truncation. Anything longer risks being cut on smaller screens.
• Body / description text: front-load meaning. Assume the reader sees only the first line before deciding to keep reading.
• Call to action: Reddit provides a set of standard CTA button options (Learn More, Shop Now, Sign Up, and similar). Pick the one that matches the action, do not try to smuggle the CTA into the headline.
• URL / display: use clean, trackable destination URLs with your UTM parameters attached so attribution works downstream.

Getting Through Review the First Time

Specs are only half the battle. These practical rules prevent the avoidable rejections:

• No misleading claims or fake UI. Buttons in the creative that imply interactivity, or exaggerated claims, get flagged.
• Respect prohibited and restricted categories. Some verticals face extra requirements or outright limits. Check before you build the whole campaign.
• Keep text overlay reasonable. Heavily text-covered images read as spam and can suppress delivery even when technically accepted.
• Match the landing page to the ad. A destination that does not deliver what the ad promised is both a review risk and a conversion killer.

Pre-Flight Checklist

Before you hit upload, confirm:

1. Aspect ratio matches your primary placement (1:1 is the safe default).
2. Resolution is high enough to look crisp on retina screens.
3. File type and size are within accepted limits.
4. Video hook lands in two seconds, muted, with burned-in captions.
5. Headline reads cleanly under the display limit with no truncation.
6. Destination URL is correct, trackable, and matches the ad’s promise.
7. Creative respects Reddit’s content policies for your category.

Run that list every time and your creatives clear review on the first pass, which means your campaigns launch on schedule instead of stalling on a technicality. For the exact, current numbers on any given day, Reddit Ads Manager is the source of truth. This sheet is the map that gets you there fast.

If you are still deciding which format to build for, start with our guide to Reddit ad formats instead, and see how much Reddit ads cost before you commit a budget. We also run all of this for brands as a Reddit Ads agency.