Suppose if I use any external link to upload image in posts .What is the difference in external image link and wordpress attachment . If the image will optimize is google whose site will appear in image search if the image is in my post through external link.
Using an external link for images, means that your wordpress blog is not hosting them at all. So if the external link goes bad for any reason, you lost your image. For google, most likely the external image will be in their searches and not your blog. Why I upload images to my wordpress blogs. I can name the images whatever I want. Thus google will find the image title and bam...links back to my blog.
Using Internal or External don't matter... the most important is the ALT and Title tags... on some of my blogs i use external images... they appear in Search result and link Directly to my Blog Post... So External or Internal Image Link is not the Problem you can care about, but a good images Optimization...
Curiously, I am not entirely sure on this. I will have to check a few things but both iowadawg and themesforall make very valid points. The thing is, I am not sure iowa's thoughts take stuff like a CDN into consideration in today's web landscape. Good question though, I will see what, if any internal metrics I have on this. I typically have clients host images internally as well but they are usually to lazy to deal with them correctly lol.. At the end of the day it may not make that much of a difference. It will further be influenced by what the images are or represent. There may be some inherent brand related differences if you are a photographer for instance. It frankly just makes sense to serve things from multiple points due to speed being a ranking signal now. Nigel