Compare
Pick two instruments; both are drawn as percentage change from the start of the period, on one chart. Your choice lives in the address, so whoever you send the link to opens the same comparison.
What is compared is the change. Both lines show percentage change from the first day the two have in common; two prices in different currencies on one axis would be a picture of nothing.
This page does not say which one is better, and cannot — it shows what happened, not what will. Why we never say which way — in the FAQ.
Why percentages, not prices?
Gram gold is measured in thousands, the dollar in tens. Putting both on one axis as prices would show the big one as a mountain and the small one as a flat line — a picture of a question nobody asked. Both lines carry the percentage change from the first day the two have in common; that is the only thing that can be compared.
The timeline is the intersection of the two series: only the days on which both were observed are drawn. Silver's record is young, so comparisons with silver show a shorter window — and showing it short is more honest than making it up.
Pairs people look at
Gram gold / DollarGram gold / EuroBitcoin / Ounce of goldGold / SilverDollar / Euro