March 27, 2026
You scanned a document and tried to send it on LINE or Discord, only to be told the file is too large. Different messaging apps have wildly different file size limits -- some let you send 2GB, while others cap free users at just 10MB. This page puts all the limits in one table so you have a quick reference next time.
File Size Limits by Platform
| Platform | Free Tier | Paid Tier | Notes |
|---|---|---|---|
| LINE | ~1GB | - | Not explicitly documented by LINE; files expire after a limited time |
| Slack | 1GB / file | 1GB / file (same) | Free plan has 90-day message visibility limit |
| Microsoft Teams | 100MB (inline chat) | 250GB (via OneDrive) | Files tab uses OneDrive with 250GB limit |
| Discord | 10MB | 50MB (Nitro Basic) / 500MB (Nitro) | Lowered from 25MB in September 2024 |
| 2GB | - | Raised from 100MB in 2022; use Wi-Fi for large files | |
| Facebook Messenger | 100MB | - | Raised from 25MB in April 2025 |
| Telegram | 2GB | 4GB (Premium) | Free users can download 4GB files from Premium users |
The most common pain point: Discord free tier is only 10MB. In September 2024, Discord cut its free limit from 25MB to 10MB. A scanned PDF can easily exceed this. If you regularly share files on Discord, compression is almost always necessary.
From Most Generous to Most Restrictive
- WhatsApp, Telegram (2GB) -- file size is virtually never a concern
- LINE, Slack (~1GB) -- you are unlikely to hit these limits in normal use
- Teams (100MB chat / 250GB files tab) -- the 100MB inline limit catches people occasionally
- Messenger (100MB) -- recently raised, sufficient for most cases
- Discord (10MB free) -- you will almost certainly hit this limit
Platform-Specific Tips
Discord users: 10MB is very tight. A 5-page color scan can easily be 40MB. Use PDF Under's compress tool and set your target to 8MB for a safe buffer. For documents over 10 pages, consider splitting into parts and sending separately.
Teams users: If the 100MB inline chat limit is blocking you, upload via the Files tab in your channel instead. This routes through OneDrive and supports up to 250GB. This is the recommended path for large work reports.
LINE users: The limit is generous, but be aware that LINE does not keep files on its servers permanently. If the recipient does not download within the retention period, the file expires. For important documents, send a backup via email as well.
WhatsApp users: The 2GB limit is rarely an issue, but when sending large files, make sure both parties are on Wi-Fi to avoid consuming mobile data.
Getting the Best PDF Quality Within Size Limits
When you need to compress a PDF to fit a platform limit, the goal is not just to make it smaller -- it is to keep as much quality as possible within the allowed size. The key factor is DPI (resolution) and how much space each page gets.
How DPI Affects File Size
For A4-sized pages, approximate file size per page:
| DPI | Color (per page) | Grayscale (per page) |
|---|---|---|
| 150 DPI | ~200-400KB | ~80-150KB |
| 200 DPI | ~400-800KB | ~150-300KB |
| 300 DPI | ~800KB-2MB | ~300-600KB |
Calculating Your Per-Page Budget
The formula is simple: target size / number of pages = per-page budget.
Example: you need to send a 10-page PDF on Discord, targeting 8MB. Your per-page budget is 800KB. Looking at the table above, 800KB is roughly equivalent to 200 DPI color or 300 DPI grayscale -- both produce clear, readable results.
For a 30-page document at 8MB, each page gets only 267KB. At that point, color documents need to drop to 150 DPI, or you should consider grayscale.
Recommendations by Document Type
- Text-heavy documents (contracts, reports, letters): 150 DPI grayscale is sufficient. Text remains crisp on screen. This is the most space-efficient option
- Mixed content (presentations, product catalogs): 200 DPI color strikes a good balance between text clarity and image quality
- Image-heavy documents (portfolios, photo collections): Use 200-300 DPI color. If space is tight, reduce page count rather than resolution
- Scanned documents: If you can re-scan, scan at the appropriate DPI directly -- this produces better results than compressing a high-DPI scan. Use 150 DPI grayscale for text, 200 DPI color for documents with images
When setting your target size in PDF Under's compress tool, aim for 90% of the platform limit -- for example, set 8MB for Discord's 10MB limit to leave a safety margin.
What Resolution Do You Need for Mobile Viewing?
Phone screens are typically 5-7 inches. Even at high display resolutions (2K or 4K), the small screen size means a 150 DPI PDF already looks sharp. You do not need 300 DPI for mobile viewing -- that resolution is designed for printing.
If the recipient will primarily view the PDF on their phone (not print it), 150-200 DPI is more than enough and saves significant file size.