Difference between Indispensable and Obligatory

INDISPENSABLE vs OBLIGATORY: NOUN

A bag or pocket, frequently of silk and much decorated, worn by women in the first years of the nineteenth century, on the outside of the gown, instead of inside, as an ordinary pocket would be.
Specifically, trousers.
An indispensable person or thing.
One that is indispensable.

Required by obligation or compulsion or convention
Morally or legally constraining or binding
Of the nature of an obligation; compulsory.
Required as part of a routine course of action or cultural expectation; predictable.
Obligate.
Binding in law or conscience; imposing duty or obligation; requiring performance or forbearance of some act; -- often followed by on or upon.
Imposing obligation, morally or legally; binding: an obligatory promise.
Requiring a matter or obligation.

Not to be set aside, evaded, or escaped; inevitable.
Not to be dispensed with; not to be omitted or spared; absolutely necessary or requisite.
Not permissible by dispensation or license; incapable of being legalized.
Vitally necessary
Absolutely necessary
Essential
Not to be dispensed with

Imposing obligation; binding in law or conscience; imposing duty; requiring performance of or forbearance from some act: followed by on before the person, formerly by to.

Prerequisite, Paramount, Dispensable, Necessity, Imperative, Irreplaceable, Crucial, Important, Invaluable, Integral, Obligatory, Critical, Necessary, Vital, Essential

Statutory, Minimum, Requirement, Mandated, Obliged, Incumbent on, Imposed, Bounden, Indispensable, Necessary, Prerequisite, Required, De rigueur, Mandatory, Compulsory

Prerequisite, Paramount, Dispensable, Necessity, Imperative, Irreplaceable, Crucial, Important, Invaluable, Integral, Obligatory, Critical, Necessary, Vital, Essential

Statutory, Minimum, Requirement, Mandated, Obliged, Incumbent on, Imposed, Bounden, Indispensable, Necessary, Prerequisite, Required, De rigueur, Mandatory, Compulsory

But it is not obligatory in this case.
Obligatory use of local labor, plant and material.
APA the cover page is not always obligatory.
Obligatory committees needed to do businessaudit, budget etcvi.
Telugu Meaning of Obligatory or Meaning of Obligatory in Telugu.
This Act applies to obligatory insurance contracts with the specifications arising from the Act which establishes obligatory insurance.
The state obligatory standards of relevant levels of education are obligatory for all educational organizations irrespective of their form of ownership, types and kinds.
If one is performing dry ablution for an obligatory prayer, one must intend its being obligatory, though need not specify whether.
It shows that circumcision was obligatory upon him and therefore obligatory on all men.
But I feel this obligatory part is looking a lot less obligatory.