Blog ·Guides ·6 min read ·Updated July 8, 2026
How to Reduce File Size: The Complete Guide (Images, PDF, Video, Audio)
"The file is too large." It is one of the most common frustrations online — an email that bounces, an upload that stalls, a form that rejects your document. The good news is that almost any file can be made dramatically smaller without ruining it, once you know which lever to pull for each type. Here is the complete, practical guide.
Why files get so big
Files are usually larger than they need to be because they store more detail than you will ever use. A phone photo holds far more resolution than a screen can show; a PDF embeds full-resolution scans; a video keeps a high bitrate even when it will be watched in a small window. Reducing file size means trimming this hidden excess — either by compressing (lowering quality by an amount you cannot perceive) or by resizing (reducing the actual dimensions or resolution).
Images
Two levers: compress and resize. Compressing a JPG at around 70–80% quality removes most of the file size with no visible change. Resizing matters just as much — if a photo will only ever appear 1200 pixels wide, there is no reason to keep it at 6000. Do both and a photo can drop by 80–95%. For the web, converting to WebP shrinks it further still.
PDFs
Most oversized PDFs are heavy because of high-resolution images and embedded fonts inside them. A PDF compressor lowers image resolution and optimises the file structure, often cutting 50–90% from image-heavy documents like scans and brochures. Text-only PDFs are already small and will compress less. If it is still too big to email, split it into parts or share a download link instead.
Video & audio
Video is the biggest offender. The two levers are resolution and bitrate: dropping 4K to 1080p (or 1080p to 720p) is the single largest saving and is often invisible on phones, while lowering the bitrate trims further — go too far and fast motion looks blocky, so reduce gradually. For audio, lowering the bitrate is usually enough: 128 kbps is plenty for speech, 192–320 kbps for music. And if you only need the sound from a video, extracting it to MP3 discards the video entirely.
A quick reference
Where to start for each file type:
| File type | First lever | Then |
|---|---|---|
| Photo / image | Compress to 70–80% quality | Resize to the size you actually need |
| Run a PDF compressor | Split, or share a link if still large | |
| Video | Lower the resolution | Reduce the bitrate gradually |
| Audio | Lower the bitrate | Trim unused sections |
One habit that saves you every time
Always keep your original file and work from a copy. Compression is a one-way street — you can always make a smaller version from a high-quality master, but you can never restore detail once it has been removed. Compress for sending; keep the original for safekeeping. Every tool mentioned here is available, free, in The App Hub Converter.
Frequently asked questions
Does reducing file size always reduce quality?
Not noticeably. At sensible settings the change is invisible or inaudible. Quality only suffers visibly when you compress very aggressively or repeatedly.
What is the difference between compressing and resizing?
Compressing lowers quality intelligently to save space; resizing reduces the actual pixel dimensions or resolution. Combining both gives the smallest file.
Why is my file still too big after compressing?
It may already be near its minimum, or the wrong lever was used — for a huge photo, resize as well as compress; for a long video, lower the resolution; for a large PDF, split it.
Try it yourself — free
The App Hub Converter runs in your browser: private by default, no sign-up, files auto-deleted.
Open the Converter