The extension and actual image format are different
The file extension is the end of the name, and the actual format is the data structure stored within the file. Even if you rename a PNG file to JPG, the internal data remains the same. Depending on the app, it may recognize the internal format and open it, but the upload service may reject files whose extension and actual format do not match.
JPG and JPEG are extensions that refer to the same JPEG format. There is no need to recompress the same format if you are just renaming JPG to JPEG. Conversely, switching between PNG and JPEG requires re-encoding of the data.
Principle of converting images in browser
This tool checks the format markers at the beginning of the file and decodes the image in the browser. Draw the decoded pixels on a Canvas of the same size as the original and create a new file with a PNG, JPEG, or WebP encoder. Even if the original pixel size is maintained, the storage method changes, so the number of bytes and quality of the file may vary.
Output is produced by HTMLCanvasElement.toBlob. If you request an unsupported output format, the browser may fallback to PNG, so the tool also checks that the MIME type of the returned file matches the selected format. If there is a discrepancy, we will not provide you with a download and will guide you to select a different format.
How to change PNG to JPG
- Select the original PNG in the Change Image Extension tool.
- Select JPEG for Convert to format and set a quality value. The initial value is 85 and the range is 10 to 100.
- Tap Convert Image Format and check the preview and number of bytes before and after conversion.
- Click Download Conversion File to save the .jpg file. The original files remain separate.
When changing JPG to PNG or WebP to JPG, you only need to select a different output format. If you change settings or input files, the old results link will disappear, so convert again to the new conditions. The Processing Completed message does not mean that the downloaded file has been saved to the actual disk. Check your browser to see where it is saved and whether it is complete.
Choose based on transparency and compression method
PNG uses lossless compression and supports transparency. Typical JPEG storage is lossy compression and does not support transparency. WebP is a format that supports lossy and lossless compression and transparency, but this tool does not have the ability to select WebP lossless mode.
Selecting a JPEG in Moyoutil fills transparent areas with white. If you want to maintain transparency in your logo or background removal results, use PNG or WebP. Quality input is disabled in PNG, and the quality number in JPEG/WebP is an encoder setting and does not guarantee a percentage of image quality compared to the original.
Input restrictions and information not preserved
Input and output formats are PNG, JPEG, and WebP. Input is limited to a maximum of 20 MB, 25 million pixels, and 8,192 pixels each horizontal and vertical. Files are processed one by one and HEIC, GIF, SVG and AVIF are not supported by this tool. Conversion may fail if the file is corrupted or unreadable by your browser.
The result is a still image. Preservation of animation movement and metadata such as EXIF and original color profile is not supported. If this information is important to you, such as for archiving or printing, keep the original and use an editor that suits your purpose. Photos are processed within the browser without being uploaded to the tool's servers.
How to check the file after conversion
Reopen the saved file and check the size, edges, transparent areas, and small text. Saving as PNG does not bring back any details lost from previous JPEG compression. Saving with the same JPEG repeatedly can also add to the loss, so if possible, convert from the original you first saved.
Extension conversion alone does not guarantee target capacity. If you exceed the upload limit, use the image resizing tool to reduce it to the required pixel size or adjust the quality of JPEG/WebP and compare the results. You must finally check whether the site you are submitting to meets all of its format, size, and capacity requirements.
Frequently Asked Questions
Can I convert files with only the extension changed?
Rather than relying solely on names or MIME notations, the tool checks file markings and browser decoding results for PNG, JPEG, and WebP. If the internal data is in a supported format, it can be processed, but renaming unsupported files will not result in conversion functionality.
Does conversion necessarily reduce the capacity?
No. It may be larger depending on the output format, quality, original compression status and image content. Check the preview and the number of bytes before and after conversion.