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cnvrt.tools Help Guide

Convert images, videos, audio, and documents instantly in your browser. Everything happens locally on your device - no uploads required.

Quick Start

  1. Drag & drop files onto the conversion area or click to select files
  2. Files convert automatically based on your current format and quality settings
  3. Download starts once conversion completes

Batch conversion: Mix different file types in one batch - each will convert to its appropriate output format.

Droplet Mode (URL Shortcuts)

Create conversion shortcuts using URL parameters:

https://cnvrt.tools/[format]-[parameters]

  • /webp-q80 - Convert to WebP at 80% quality
  • /mp4-w720-h480 - Convert video to 720x480 MP4
  • /mp3-nb - Convert audio to MP3 with broadcast normalization (-23 LUFS)
  • /pdf - Convert documents to PDF

Copy URLs from the settings panel for easy bookmarking.

🖥️ Desktop (Best Performance)

  1. Firefox - Fastest FFmpeg WebAssembly performance with SharedArrayBuffer
  2. Chrome/Edge - Good performance, excellent compatibility
  3. Safari - Functional but typically slower
⚠️ Desktop Limitations:
  • File size limits range from 500MB to 1.5GB depending on a number of factors
  • May not work on older devices and browsers

📱 Mobile (Limited Performance)

  • Chrome Mobile - Best mobile performance
  • Safari iOS - Good for smaller files
  • Firefox Mobile - Decent performance
⚠️ Mobile Limitations:
  • Much smaller file size limits (typically 50-200MB max)
  • Slower processing speeds, especially in low power modes
  • May crash with complex videos or large documents
  • Battery drain during intensive conversions
  • May not work on older devices and browsers

Progressive Web App (PWA)

cnvrt.tools can be installed as a standalone app:

  • Desktop: Look for install icon in browser address bar
  • Mobile: Use "Add to Home Screen" from browser menu
  • Benefits: Faster access, fullscreen experience, offline capability

Images

Input: JPG, PNG, WebP, GIF, AVIF, TIFF, BMP, HEIC/HEIF, SVG, ICO, PSD

Output: JPG, PNG, WebP, GIF, AVIF, TIFF, BMP, HEIC/HEIF, ICO

Video

Input: MP4, WebM, AVI, MKV, MOV, FLV, MPEG, and more

Output: MP4, WebM, AVI, MKV, MOV, Animated GIF

Audio

Input/Output: MP3, WAV, AAC, OGG, FLAC, M4A, WMA

Documents

Input: PDF, DOCX, DOC, EPUB, HTML, Markdown, RTF, TXT

Output: PDF, DOCX, EPUB, HTML, Markdown, RTF, TXT

Note: Document conversion pipelines are actively improving and may change.

Additional Formats: FFmpeg supports many more formats beyond those listed. We'll attempt to process other file types, with a notification if unsuccessful.

🚨 Conversion & Processing Issues

ProblemPossible CauseSolution
Conversion fails or crashesFile too large or complex
  • Use smaller files (under 500MB desktop, 100MB mobile)
  • Lower quality settings in settings panel
  • Try converting one file at a time
  • Close other browser tabs and windows
Page becomes unresponsiveBrowser memory limit exceeded
  • Refresh page to reset FFmpeg, or clear browser cache and cookies to get a fresh start
  • Close other browser tabs
  • Switch to another browser for better performance
Video conversion extremely slowHigh resolution or complex video
  • Lower video resolution in settings
  • Use "fast" or "faster" quality preset
  • Convert to lower bitrate
Audio missing from videoCodec or format incompatibility
  • Try different output format (MP4 is most compatible)
  • Check if original file has audio
  • Switch to "Audio Only" mode to test

📱 Mobile-Specific Issues

ProblemSolution
App crashes on mobile
  • Use files under 50MB
  • Close all other apps
  • Try Chrome mobile for best performance
Battery drains quickly
  • Convert smaller files
  • Plug in device during conversion
  • Lower quality settings
Videos won't convert on mobile
  • Avoid 4K or high-framerate videos
  • Try converting short clips first
  • Use Wi-Fi instead of cellular

📄 Document Conversion Issues

ProblemCauseSolution/Workaround
Images missing from converted documentReferenced images (file paths) cannot be accessed by browser
  • Use documents with embedded images (docx, pdf, etc.)
  • Remove relative paths to images and use hosted images when possible (html, markdown, etc.)
Converted file is huge (>100MB)Base64 embedded images create large text files
  • Use "Use Placeholders" option in document settings
  • Try converting to PDF with print dialog instead
Formatting looks wrongComplex layouts don't preserve perfectly
  • Try PDF output with print dialog
  • Use simpler document formatting when possible (there are inherent limitations to browser-based conversion).
  • Report any issues you encounter at the link below and I will attempt to fix them.
Fonts look differentSpecial fonts fall back to system defaults
  • Use common fonts (Arial, Times, etc.)
  • This is a limitation of browser-based conversion

🆘 Still Having Issues?

Reset Everything:

Refresh the page completely to reset FFmpeg and clear any corrupted state

Try Different Browser:

Firefox > Chrome/Edge > Safari for performance. Each browser handles memory differently

Clear Browser Data:

Clear cache and cookies if issues persist across sessions

Check File Integrity:

Try opening your file in another app to ensure it's not corrupted

Check File Size:

Check the file sizes and ensure they are not too large for the browser (see file size limits below).

Report Issues:

Report any issues you encounter with the here and I will attempt to fix them.

🖥️ Desktop Browsers

  • Recommended: Under 500MB per file
  • Maximum: ~1-2GB (varies by system)
  • 4K Video: Possible but slow (10+ minutes)
  • Batch Processing: 10-50 files depending on size

📱 Mobile Browsers

  • Recommended: Under 50MB per file
  • Maximum: ~100-200MB (device dependent)
  • HD Video: Limited to short clips
  • Batch Processing: 5-10 small files max

💡 Performance Tips

  • Start with small test files to gauge your device's capabilities
  • Use lower quality settings for faster processing
  • Convert large files one at a time
  • Ensure your device has sufficient battery for long conversions

Image Quality & Size

  • Quality: 1-100 (balance file size vs. quality)
  • Resize: Set max width/height (maintains aspect ratio)
  • Resize Method: Bilinear, bicubic, nearest, or lanczos algorithms

Video Encoding

  • Quality Presets: Low, medium, high (easy settings)
  • Bitrate: Higher = better quality, larger files
  • Resolution: Maintain original or choose standard sizes
  • Animated GIF: Frame rate, dithering, and size controls

Audio Processing

  • Bitrate: 64-320 kbps for compressed formats
  • Channels: Mono or stereo output
  • Sample Rate: 8kHz to 96kHz options
  • Normalization: EBU R128 compliant loudness normalization with presets for streaming, broadcast, and podcast

Document Conversion

  • PDF Generation: Choose between programmatic or browser print dialog methods
  • Format Preservation: Maintains formatting where possible between formats
  • Conversion Quality: Focus on accuracy over speed

Droplet Parameters

Each should be separated with a dash. Invalid parameters will be ignored. Any parameters that aren't provided or out of range will be set to the default value.

ParameterDescriptionApplicable FormatsExample
w[number]Max width in pixelsImages, Video, Animated GIFw1920
h[number]Max height in pixelsImages, Video, Animated GIFh1080
q[number]Quality 1-100JPG, WebP, AVIFq85
ar0 / ar1Maintain aspect ratio (0=off, 1=on)Images, Video, Animated GIFar0
rm[method]Resize method (bilinear, bicubic, nearest, lanczos)Imagesrmlanczos
cl[number]Compression level 0-9PNGcl6
co[number]Number of colors 2-256GIFco128
d0 / d1Dithering (0=off, 1=on)GIF, Animated GIFd1
e[number]Encoding effort 0-9AVIFe6
cs[format]Chroma subsampling (420, 422, 444)JPEG, WebPcs420
is[sizes]Icon sizes (comma-separated: 16,24,32,48,64,72,96,128,256)ICOis16,32,64
b[number]Bitrate in Mbps (video) or kbps (audio)Video, Audiob5
p[preset]Video encoding preset (ultrafast, superfast, veryfast, faster, fast, medium, slow, slower, veryslow)Videopfast
fps[number]Frame rate 1-30Animated GIFfps15
c[number]Audio channels (1=mono, 2=stereo)Audio, Videoc2
s[number]Sample rate in HzAudio (except FLAC)s44100
nxDisable audio normalizationAudionx
nsStreaming preset (-16 LUFS, -1 dB peak)Audions
nbBroadcast preset (-23 LUFS, -1 dB peak)Audionb
ntPodcast preset (-18 LUFS, -1 dB peak)Audiont
nl[number]Custom LUFS target (0-60, treated as negative)Audionl23
np[number]Custom peak target (0-6, treated as negative dB)Audionp1
n[number]Legacy LUFS target (0-60, treated as negative)Audion16
ps[size]Page size (a4, a3, letter, legal, tabloid)PDFpsa4
po[orientation]Page orientation (portrait, landscape)PDFpoportrait
mt[number]Margin top in points (0-200)PDFmt70
mb[number]Margin bottom in points (0-200)PDFmb70
ml[number]Margin left in points (0-200)PDFml50
mr[number]Margin right in points (0-200)PDFmr50
fs[number]Font size in points (8-24)PDFfs12
lh[number]Line height multiplier (1.0-3.0)PDFlh1.5
pn0 / pn1Show page numbers (0=off, 1=on)PDFpn1
pd0 / pd1Use print dialog (0=off, 1=on)PDFpd0
sh0 / sh1Show header (0=off, 1=on)PDFsh1
ht[text]Header text (URL encoded)PDFhtMy%20Document
ei[method]Embed images as (base64, placeholder)HTML, Markdown, EPUBeibase64
rh0 / rh1Suppress repeated headers during PDF extraction (0=off, 1=on)HTML, Markdown, EPUB, TXTrh1
rf0 / rf1Suppress repeated footers during PDF extraction (0=off, 1=on)HTML, Markdown, EPUB, TXTrf0
pi0 / pi1Embed all PDF pages as images instead of text (0=off, 1=on)HTML, Markdown, EPUB, TXTpi1
pt0 / pt1Only embed pages without text as images (0=off, 1=on)HTML, Markdown, EPUB, TXTpt1
  • No uploads: All processing happens locally in your browser
  • Private: Your files never leave your device
  • Secure: Works offline once loaded
  • Fast: No network delays for conversion processing