What an SVG is, and why it has no pixels to convert
An SVG is not a picture in the usual sense. It is an XML text file describing shapes, paths, text and gradients that a renderer draws fresh at whatever size is asked for. That is why logos and icons are exported as SVG from Figma, Illustrator and Inkscape: they stay sharp at any scale and the files are tiny. The catch is that plenty of places refuse them. Social networks, marketplace listings, many email tools, print shops and older CMS media libraries want a raster file, and JPG is the one that opens absolutely everywhere.
How the tool rasterises the file
The SVG is loaded into an ordinary image element in your browser, drawn onto a canvas, and the resulting pixels are turned into a PNG in memory before a Web Worker encodes the final JPG with mozjpeg. Two consequences follow from that path.
First, the output size in pixels comes from the SVG itself. The canvas is created at the image's intrinsic width and height, which is whatever the width and height attributes on the root element say. If those are missing, the browser may derive a size from the viewBox, and if it reports nothing usable the tool falls back to 512x512. There is no scale control on this page. To get a 2400 pixel wide JPG, open the SVG in a text editor and set the width and height attributes before converting.
Second, the image element renders the SVG in a restricted mode: scripts do not run, and external resources such as linked images, remote fonts and external stylesheets are not loaded. Text in the SVG is drawn with fonts installed on your device, so a logo set in a custom typeface will come out in a fallback font unless the designer converted the text to outlines first. Filters, gradients, masks and clip paths generally render fine.
The background problem
Most SVGs have a transparent background, and JPG has no transparency at all. Transparent pixels in canvas memory carry no colour, so after encoding they typically appear black, not white. If you want a white background, add a rectangle covering the whole canvas as the first element of the SVG, for example a <rect> with width and height of 100% and a fill of white. If transparency matters to you, this is the wrong target: use SVG to PNG and keep the alpha channel.
Quality and what JPG does to vector art
The quality slider runs from 20 to 95 with a default of 80. JPG is designed for photographs. Hard edges, thin lines and small text are its weakest material, producing faint ringing and blocky halos at lower settings. For flat vector artwork, stay at 85 or above; for illustrations with gradients and soft shading, 75 to 85 is fine.
A worked example: a 1200x630 social card SVG of 18 KB with a logo, a headline and a gradient background typically becomes a JPG of 90 to 180 KB at quality 85. A 1000x1000 flat icon on a white rectangle usually lands around 40 to 80 KB. Note that the JPG can easily be ten times larger than the SVG it came from; that is normal, because pixels are being stored where geometry used to be. Numbers like these are typical, not guaranteed.
When to keep the SVG
If the destination is a web page, an app icon set or a print job, keep the vector. It scales without loss and is usually smaller. Convert only when a specific system demands a raster, and if that system accepts PNG or WebP, prefer SVG to WebP for smaller files with transparency intact. For favicons, SVG to ICO builds a multi-resolution icon directly from the vector. Everything on this page happens locally; the SVG is never sent anywhere.