を通じて / を通して【をつうじて / をとおして】

The expressions を通じて and を通して both mean "through", "via", or "throughout", and are used in two main ways: to indicate a means or intermediary through which something is done, and to indicate a span of time throughout which something continues.

Means / Intermediary ("through," "via")

When expressing that something is accomplished by means of or via a person, organization, medium, or method, both forms can be used largely interchangeably.

This usage covers a wide range of intermediaries: people, media, activities, experiences, organizations, etc.

Throughout a period of time ("throughout," "all through")

When expressing that something applies or continues throughout an entire period, both forms can be used, though を通じて is slightly more common for this meaning.

Nuance differences

While the two forms are often interchangeable, there are tendencies:

• を通して leans slightly more toward the concrete image of physically or literally "passing through" something – an intermediary person, a specific channel.
• を通じて is slightly more common for abstract means and for the temporal "throughout" usage.

In practice, native speakers use both forms freely in most contexts, and choosing one over the other rarely causes a difference in meaning.