The web uploader is easily accessible from the web app once you've logged in. Use it for manual upload—when your images are located on an external camera, a memory card, or on your hard drive rather than on your mobile device. Also, the web uploader allows for editing the placement of your images before uploading. Finally, by connecting your computer to the web using an Ethernet cable, the web uploader can process your images at a faster rate than a WiFi connection on the same computer or on a mobile device.
When you've entered the web uploader, you can choose which files to upload. Your images need to have a timestamp as well as location information attached to them (in the image EXIF data). If this is not the case, the web uploader will prompt you and you have the chance to manually locate the images to their correct positions on the map. Ideally, the EXIF data also contains information about the compass angle, but upload is possible even without it. In that case, the images will be assigned a compass angle value of -1 in our database and will be displayed as north on the map. You can edit that post-upload.
The upload process on the web goes in two steps: 1) you upload your images into what you could call a "bucket" that is related to your account, and 2) you publish the images gathered up in your bucket which tells Mapillary to start processing them and put them on the map.
In the first step, the bucket will recognize if you are trying to add images that are already there and will prompt you about it. This is just for your information, nothing extra that you need to do. The bucket will remember the images even if you refresh the page or exit the uploader and enter again, or even close and reopen the tab. Therefore, if your upload stalls/fails half way through this step, but part of the images have already reached the bucket, then you can just refresh and add the whole batch of images again, and it will all be sorted out for you—nothing will be added twice.
When you’re done uploading images, you need to publish them. When you hit the button to publish, you also erase the memory of the bucket. Now you need to make sure yourself that you don't upload and publish the same images again.
You might want to publish your files in batches rather than in bulk because the web uploader turns one upload into one sequence. An automatic bot will run later to cut the sequences where images are too far apart, but you should be aware that this can take up to a few days. Also, you may have a different logic about how your images should be arranged into sequences, so publishing in separate batches will give you full control over that.