opinion: Mr. Justice Douglas
  delivered the opinion of the Court.
  The Halveys were married in 1937 and lived together in New York until 1944. In 1938 a son was born. Marital troubles developed. In 1944 Mrs. Halvey, without her husband’s consent, left home with the child, went to Florida, and established her residence there. In 1945 she instituted a suit for divorce in Florida. Service of process on Mr. Halvey was had by publication, he making no appearance in the action. The day before the Florida decree was granted, Mr. Halvey, without the knowledge or approval of his wife, took the child back to New York. The next day the decree was entered by the Florida court, granting Mrs. Halvey a divorce and awarding her the permanent care, custody, and control of the child.
  Thereupon she brought this habeas corpus proceeding in the New York Supreme Court, challenging the legality of Mr. Iialvey’s detention of the child. After hearing, the New York court ordered (1) that the custody of the child remain with the mother; (2) that the father have rights of visitation including the right to keep the child with him during stated vacation periods in each year, and (3) that the mother file with the court a surety bond in the sum of $5,000, conditioned on the delivery of the child in Florida for removal by the father to New York for the periods when he had the right to keep the child with him. 185 Misc. 52, 55 N. Y. S. 761. Both the Appellate Division, 269 App. Div. 1019, 59 N. Y. S. 2d 396, and the Court of Appeals, 295 N. Y. 836, 66 N. E. 2d 851, affirmed without opinion. The case is here on a petition for a writ of certiorari which we granted because it presented an important problem under the Full Faith and Credit Clause of the Constitution. Article IV, § 1.
  The custody decree was not irrevocable and unchangeable; the Florida court had the power to modify it at all times. Under Florida law the “welfare of the child” is the “chief consideration” in shaping the custody decree or in subsequently modifying or changing it. Frazier v. Frazier, 109 Fla. 164, 169, 147 So. 464, 466; See Phillips v. Phillips, 153 Fla. 133, 134-135, 13 So. 2d 922, 923. But “the inherent rights of parents to enjoy the society and association of their offspring, with reasonable opportunity to impress upon them a father’s or a mother’s love and affection in their upbringing, must be regarded as being of an equally important, if not controlling consideration in adjusting the right of custody as between parents in ordinary cases.” Frazier v. Frazier, 109 Fla., p. 169, 147 So., p. 466. Facts which have arisen since the original decree are one basis for modification of the custody decree. Frazier v. Frazier, 109 Fla., p. 168, 147 So., p. 465; Jones v. Jones, 156 Fla. 524, 527, 23 So. 2d 623, 625. But the power is not so restricted. It was held in Meadows v. Meadows, 78 Fla. 576, 83 So. 392-393, that “the proper custody of the minor child is a proper subject for consideration by the chancellor at any time, even if facts in issue could have been considered at a previous hearing, if such facts were not presented or considered at a former hearing.” (Italics added.) Or, as stated in Frazier v. Frazier, 109 Fla., p. 168, 147 So., p. 465, a custody decree “is not to be materially amended or changed afterward, unless on altered conditions shown to have arisen since the decree, or because of material facts bearing on the question of custody and existing at the time of the decree, but which were unknown to the Court and then only for the welfare of the child.” The result is that custody decrees of Florida courts are ordinarily not res judicata either in Florida or elsewhere, except as to the facts before the court at the time of judgment. Minick v. Minick, 111 Fla. 469, 490-491, 149 So. 483, 492.
  Respondent did not appear in the Florida proceeding. What evidence was adduced in that proceeding bearing on the welfare of the child does not appear. But we know that the Florida court did not see respondent nor hear evidence presented on his behalf concerning his fitness or his claim “to enjoy the society and association” of his son. Frazier v. Frazier, 109 Fla., p. 169, 147 So., p. 466. It seems to us plain, therefore, that under the rule of Meadows v. Meadows, supra, the Florida court would have been empowered to modify the decree in the interests of the child and to grant respondent the right of visitation, if he had applied to it rather than to the New York court and had presented his version of the controversy for the first time in his application for modification.
  So far as the Full Faith and Credit Clause is concerned, what Florida could do in modifying the decree, New York may do. Article IV, § 1 of the Constitution provides that “Full Faith and Credit shall be given in each State to the public Acts, Records, and judicial Proceedings of every other State. And the Congress may by general Laws prescribe the Manner in which such Acts, Records and Proceedings shall be proved, and the Effect thereof.” Congress by the Act of May 26, 1790, c. 11, as amended, R. S. § 905, 28 U. S. C. § 687 declared that judgments “shall have such faith and credit given to them in every court within the United States as they have by law or usage in the courts of the State from which they are taken.” The general rule is that this command requires the judgment of a sister State to be given full, not partial, credit in the State of the forum. See Davis v. Davis, 305 U. S. 32; Williams v. North Carolina, 317 U. S. 287. But a judgment has no constitutional claim to a more conclusive or final effect in the State of the forum than it has in the State where rendered. See Reynolds v. Stockton, 140 U. S. 254, 264. If the court of the State which rendered the judgment had no jurisdiction over the person or the subject matter, the jurisdictional infirmity is not saved by the Full Faith and Credit Clause. See Thompson v. Whitman, 18 Wall. 457; Griffin, v. Griffin, 327 U. S. 220. And if the amount payable under a decree—as in the case of a judgment for alimony—is discretionary with the court which rendered it, full faith and credit does not protect the judgment. Sistare v. Sistare, 218 U. S. 1, 17. Whatever may be the authority of a State to undermine a judgment of a sister State on grounds not cognizable in the State where the judgment was rendered (Cf. Williams v. North Carolina, 325 U. S. 226, 230), it is clear that the State of the forum has at least as much leeway to disregard the judgment, to qualify it, or to depart from it as does the State where it was rendered.
  In this case the New York court, having the child and both parents before it, had a full hearing and determined that the welfare of the child and the interests of the father warranted a modification of the custody decree. It is not shown that the New York court in modifying the Florida decree exceeded the limits permitted under Florida law. There is therefore a failure of proof that the Florida decree received less credit in New York than it had in Florida.
  The narrow ground on which we rest the decision makes it unnecessary for us to consider several other questions argued, e. g., whether Florida at the time of the original decree had jurisdiction over the child, the father having removed him from the State after the proceedings started but before the decree was entered; whether in absence of personal service the Florida’ decree of custody had any binding effect on the husband; whether the power, of New York to modify the custody decree was greater than Florida’s power; whether the State which has jurisdiction over the child may, regardless of a custody decree rendered by another State, make such orders concerning custody as the welfare of the child from time to time requires. On all these problems we reserve decision.
  Affirmed.
  Mr. Justice Jackson concurs in the result on the ground that the record before us does not show jurisdiction in the Florida court.
  “In any suit for divorce or alimony, the court shall have power at any stage of the cause to make such orders touching the care, custody and maintenance of the children of the marriage, and what, if any, security to be given for the same, as from the circumstances of the parties and the nature of the case may be fit, equitable and just, and such order touching their custody as their best spiritual as well as other interests may require.” Fla. Stats. (1941) § 65.14.
  The legal domicile of the child is usually the domicile of his father. Minick v. Minick, 111 Fla., p. 490, 149 So., p. 492; Dorman v. Friendly, 146 Fla. 732, 738, 1 So. 2d 734, 736. The power of the Florida courts to award custody of a child is dependent either on the child being legally domiciled in Florida or physically present there. Dorman v. Friendly, supra; State ex rel. Clark v. Clark, 148 Fla. 452, 4 So. 2d 517.